Lazy<T> Oluşturucular

Tanım

Ad Alanı:

System

Bütünleştirilmiş Kod:

System.Runtime.dll

Lazy<T> sınıfının yeni bir örneğini başlatır.

Aşırı Yüklemeler

Lazy<T>()	Lazy<T> sınıfının yeni bir örneğini başlatır. Yavaş başlatma gerçekleştiğinde, hedef türün parametresiz oluşturucu kullanılır.
Lazy<T>(Boolean)	Lazy<T> sınıfının yeni bir örneğini başlatır. Yavaş başlatma gerçekleştiğinde, hedef türün parametresiz oluşturucu ve belirtilen başlatma modu kullanılır.
Lazy<T>(Func<T>)	Lazy<T> sınıfının yeni bir örneğini başlatır. Gecikmeli başlatma gerçekleştiğinde, belirtilen başlatma işlevi kullanılır.
Lazy<T>(LazyThreadSafetyMode)	T parametresiz oluşturucuyu ve belirtilen iş parçacığı güvenliği modunu kullanan Lazy<T> sınıfının yeni bir örneğini başlatır.
Lazy<T>(T)	Lazy<T> sınıfının önceden tanımlanmış bir değer kullanan yeni bir örneğini başlatır.
Lazy<T>(Func<T>, Boolean)	Lazy<T> sınıfının yeni bir örneğini başlatır. Gecikmeli başlatma gerçekleştiğinde, belirtilen başlatma işlevi ve başlatma modu kullanılır.
Lazy<T>(Func<T>, LazyThreadSafetyMode)	Belirtilen başlatma işlevini ve iş parçacığı güvenliği modunu kullanan Lazy<T> sınıfının yeni bir örneğini başlatır.

Lazy<T>()

Kaynak:

Lazy.cs

Lazy<T> sınıfının yeni bir örneğini başlatır. Yavaş başlatma gerçekleştiğinde, hedef türün parametresiz oluşturucu kullanılır.

public:
 Lazy();

public Lazy ();

Public Sub New ()

Örnekler

Aşağıdaki örnekte bu oluşturucunun kullanımı gösterilmektedir. Ayrıca Lazy<T>(Boolean) oluşturucunun (isThreadSafeiçin true belirtme) ve Lazy<T>(LazyThreadSafetyMode) oluşturucunun (modeiçin LazyThreadSafetyMode.ExecutionAndPublication belirtme) kullanımını gösterir. Farklı bir oluşturucuya geçmek için açıklama satırı yapılan oluşturucuları değiştirmeniz gerekir.

Örnek, birkaç iş parçacığından biri tarafından yavaş başlatılacak bir LargeObject sınıfı tanımlar. Bu örnekteki iki anahtar kod satırı başlatıcının oluşturulması ve gerçek başlatmadır. Main yönteminin başında, örnek LargeObjectiçin iş parçacığı güvenli gecikme başlatıcısı oluşturur:

lazyLargeObject = new Lazy<LargeObject>();

// The following lines show how to use other constructors to achieve exactly the
// same result as the previous line:
//lazyLargeObject = new Lazy<LargeObject>(true);
//lazyLargeObject = new Lazy<LargeObject>(LazyThreadSafetyMode.ExecutionAndPublication);

let lazyLargeObject = Lazy<LargeObject>()

// The following lines show how to use other constructors to achieve exactly the
// same result as the previous line:
//     let lazyLargeObject = Lazy<LargeObject>(true)
//     let lazyLargeObject = Lazy<LargeObject>(LazyThreadSafetyMode.ExecutionAndPublication)

lazyLargeObject = New Lazy(Of LargeObject)()

' The following lines show how to use other constructors to achieve exactly the
' same result as the previous line: 
'lazyLargeObject = New Lazy(Of LargeObject)(True)
'lazyLargeObject = New Lazy(Of LargeObject)(LazyThreadSafetyMode.ExecutionAndPublication)

Örnek, bir ManualResetEvent nesnesi üzerinde blok oluşturan üç iş parçacığı oluşturur ve başlatır, böylece örnek iş parçacıklarını tek seferde serbest bırakabilir. Üç iş parçacığı tarafından kullanılan ThreadProc yöntemi, LargeObject örneğini almak için Value özelliğini çağırır:

LargeObject large = lazyLargeObject.Value;

let large = lazyLargeObject.Value

Dim large As LargeObject = lazyLargeObject.Value

Lazy<T> sınıfı, yalnızca bir iş parçacığının LargeObject örneği oluşturmasına izin vermek için kilitleme sağlar. Örnek, diğer iş parçacıklarının tümünün aynı örneği elde ettiğini gösterir.

Not

Kolaylık olması için, bu örnekte Lazy<T>genel bir örneği kullanılır ve tüm yöntemler static (Visual Basic'teShared) kullanılır. Bunlar gecikmeli başlatma kullanımına yönelik gereksinimler değildir.

using System;
using System.Threading;

class Program
{
    static Lazy<LargeObject> lazyLargeObject = null;

    static void Main()
    {
        // The lazy initializer is created here. LargeObject is not created until the
        // ThreadProc method executes.
        lazyLargeObject = new Lazy<LargeObject>();

        // The following lines show how to use other constructors to achieve exactly the
        // same result as the previous line:
        //lazyLargeObject = new Lazy<LargeObject>(true);
        //lazyLargeObject = new Lazy<LargeObject>(LazyThreadSafetyMode.ExecutionAndPublication);

        Console.WriteLine(
            "\r\nLargeObject is not created until you access the Value property of the lazy" +
            "\r\ninitializer. Press Enter to create LargeObject.");
        Console.ReadLine();

        // Create and start 3 threads, passing the same blocking event to all of them.
        ManualResetEvent startingGate = new ManualResetEvent(false);
        Thread[] threads = { new Thread(ThreadProc), new Thread(ThreadProc), new Thread(ThreadProc) };
        foreach (Thread t in threads)
        {
            t.Start(startingGate);
        }

        // Give all 3 threads time to start and wait, then release them all at once.
        Thread.Sleep(100);
        startingGate.Set();

        // Wait for all 3 threads to finish. (The order doesn't matter.)
        foreach (Thread t in threads)
        {
            t.Join();
        }

        Console.WriteLine("\r\nPress Enter to end the program");
        Console.ReadLine();
    }

    static void ThreadProc(object state)
    {
        // Wait for the signal.
        ManualResetEvent waitForStart = (ManualResetEvent) state;
        waitForStart.WaitOne();

        LargeObject large = lazyLargeObject.Value;

        // The following line introduces an artificial delay to exaggerate the race condition.
        Thread.Sleep(5);

        // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
        //            object after creation. You must lock the object before accessing it,
        //            unless the type is thread safe. (LargeObject is not thread safe.)
        lock(large)
        {
            large.Data[0] = Thread.CurrentThread.ManagedThreadId;
            Console.WriteLine("Initialized by thread {0}; last used by thread {1}.",
                large.InitializedBy, large.Data[0]);
        }
    }
}

class LargeObject
{
    int initBy = 0;
    public int InitializedBy { get { return initBy; } }

    public LargeObject()
    {
        initBy = Thread.CurrentThread.ManagedThreadId;
        Console.WriteLine("LargeObject was created on thread id {0}.", initBy);
    }
    public long[] Data = new long[100000000];
}

/* This example produces output similar to the following:

LargeObject is not created until you access the Value property of the lazy
initializer. Press Enter to create LargeObject.

LargeObject was created on thread id 4.
Initialized by thread 4; last used by thread 3.
Initialized by thread 4; last used by thread 4.
Initialized by thread 4; last used by thread 5.

Press Enter to end the program
 */

open System
open System.Threading

type LargeObject() =
    let initBy = Thread.CurrentThread.ManagedThreadId
    do
        printfn $"LargeObject was created on thread id {initBy}."

    member val Data = Array.zeroCreate<int64> 100000000 with get
    member _.InitializedBy = initBy

// The lazy initializer is created here. LargeObject is not created until the
// ThreadProc method executes.
let lazyLargeObject = Lazy<LargeObject>()

// The following lines show how to use other constructors to achieve exactly the
// same result as the previous line:
//     let lazyLargeObject = Lazy<LargeObject>(true)
//     let lazyLargeObject = Lazy<LargeObject>(LazyThreadSafetyMode.ExecutionAndPublication)

let threadProc (state: obj) =
    // Wait for the signal.
    let waitForStart = state :?> ManualResetEvent
    waitForStart.WaitOne() |> ignore

    let large = lazyLargeObject.Value

    // The following line introduces an artificial delay to exaggerate the race condition.
    Thread.Sleep 5

    // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
    //            object after creation. You must lock the object before accessing it,
    //            unless the type is thread safe. (LargeObject is not thread safe.)
    lock large (fun () -> 
        large.Data[0] <- Thread.CurrentThread.ManagedThreadId
        printfn $"Initialized by thread {large.InitializedBy} last used by thread {large.Data[0]}." )

printfn """
LargeObject is not created until you access the Value property of the lazy
initializer. Press Enter to create LargeObject."""
stdin.ReadLine() |> ignore

// Create and start 3 threads, passing the same blocking event to all of them.
let startingGate = new ManualResetEvent false
let threads = [| Thread(ParameterizedThreadStart threadProc); Thread(ParameterizedThreadStart threadProc); Thread(ParameterizedThreadStart threadProc) |]
for t in threads do
    t.Start startingGate

// Give all 3 threads time to start and wait, then release them all at once.
Thread.Sleep 100
startingGate.Set() |> ignore

// Wait for all 3 threads to finish. (The order doesn't matter.)
for t in threads do
    t.Join()

printfn "\nPress Enter to end the program"
stdin.ReadLine() |> ignore

// This example produces output similar to the following:
//     LargeObject is not created until you access the Value property of the lazy
//     initializer. Press Enter to create LargeObject.
//    
//     LargeObject was created on thread id 4.
//     Initialized by thread 4 last used by thread 3.
//     Initialized by thread 4 last used by thread 4.
//     Initialized by thread 4 last used by thread 5.
//    
//     Press Enter to end the program

Imports System.Threading

Class Program
    Private Shared lazyLargeObject As Lazy(Of LargeObject) = Nothing

    Shared Sub Main()
        ' The lazy initializer is created here. LargeObject is not created until the 
        ' ThreadProc method executes.
        lazyLargeObject = New Lazy(Of LargeObject)()

        ' The following lines show how to use other constructors to achieve exactly the
        ' same result as the previous line: 
        'lazyLargeObject = New Lazy(Of LargeObject)(True)
        'lazyLargeObject = New Lazy(Of LargeObject)(LazyThreadSafetyMode.ExecutionAndPublication)


        Console.WriteLine( _
            vbCrLf & "LargeObject is not created until you access the Value property of the lazy" _
            & vbCrLf & "initializer. Press Enter to create LargeObject.")
        Console.ReadLine()

        ' Create and start 3 threads, passing the same blocking event to all of them.
        Dim startingGate As New ManualResetEvent(False)
        Dim threads() As Thread = { New Thread(AddressOf ThreadProc), 
            New Thread(AddressOf ThreadProc), New Thread(AddressOf ThreadProc) }
        For Each t As Thread In threads
            t.Start(startingGate)
        Next t

        ' Give all 3 threads time to start and wait, then release them all at once.
        Thread.Sleep(100)
        startingGate.Set()

        ' Wait for all 3 threads to finish. (The order doesn't matter.)
        For Each t As Thread In threads
            t.Join()
        Next t

        Console.WriteLine(vbCrLf & "Press Enter to end the program")
        Console.ReadLine()
    End Sub


    Private Shared Sub ThreadProc(ByVal state As Object)
        ' Wait for the signal.
        Dim waitForStart As ManualResetEvent = CType(state, ManualResetEvent)
        waitForStart.WaitOne()

        Dim large As LargeObject = lazyLargeObject.Value

        ' The following line introduces an artificial delay to exaggerate the race condition.
        Thread.Sleep(5)

        ' IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the  
        '            object after creation. You must lock the object before accessing it,
        '            unless the type is thread safe. (LargeObject is not thread safe.)
        SyncLock large
            large.Data(0) = Thread.CurrentThread.ManagedThreadId
            Console.WriteLine("Initialized by thread {0}; last used by thread {1}.", _
                large.InitializedBy, large.Data(0))
        End SyncLock
    End Sub
End Class

Class LargeObject
    Private initBy As Integer = 0
    Public ReadOnly Property InitializedBy() As Integer
        Get
            Return initBy
        End Get
    End Property

    Public Sub New()
        initBy = Thread.CurrentThread.ManagedThreadId
        Console.WriteLine("LargeObject was created on thread id {0}.", initBy)
    End Sub
    Public Data(100000000) As Long
End Class

' This example produces output similar to the following:
'
'LargeObject is not created until you access the Value property of the lazy
'initializer. Press Enter to create LargeObject.
'
'LargeObject was created on thread id 3.
'Initialized by thread 3; last used by thread 5.
'Initialized by thread 3; last used by thread 4.
'Initialized by thread 3; last used by thread 3.
'
'Press Enter to end the program

Açıklamalar

Bu oluşturucuyla oluşturulan bir örnek birden çok iş parçacığından eşzamanlı olarak kullanılabilir.

Bu oluşturucuyla başlatılan bir Lazy<T> örneğin iş parçacığı güvenlik modu LazyThreadSafetyMode.ExecutionAndPublication. İş parçacığı güvenlik modu, birden çok iş parçacığının Lazy<T> örneğini başlatmaya çalışma davranışını açıklar.

Bu oluşturucuyla oluşturulan bir Lazy<T> örneği özel durumları önbelleğe almaz. Daha fazla bilgi için Lazy<T> sınıfına veya System.Threading.LazyThreadSafetyMode numaralandırmaya bakın.

Ayrıca bkz.

• Gecikmeli Başlatma

Lazy<T>(Boolean)

Kaynak:

Lazy.cs

Lazy<T> sınıfının yeni bir örneğini başlatır. Yavaş başlatma gerçekleştiğinde, hedef türün parametresiz oluşturucu ve belirtilen başlatma modu kullanılır.

public:
 Lazy(bool isThreadSafe);

public Lazy (bool isThreadSafe);

new Lazy<'T> : bool -> Lazy<'T>

Public Sub New (isThreadSafe As Boolean)

Parametreler

isThreadSafe

Boolean

Bu örneği birden çok iş parçacığı tarafından eşzamanlı olarak kullanılabilir hale getirmek için true; Örneği aynı anda yalnızca bir iş parçacığı tarafından kullanılabilir hale getirmek için false.

Örnekler

Aşağıdaki örnek, lazily initialized nesnesine tüm erişimin aynı iş parçacığında gerçekleştiği senaryolar için iş parçacığı güvenli olmayan gecikmeli bir başlatıcı oluşturmak için bu oluşturucunun kullanımını gösterir. Ayrıca Lazy<T>(LazyThreadSafetyMode) oluşturucusunun kullanımını da gösterir (modeiçin LazyThreadSafetyMode.None belirtir. Farklı bir oluşturucuya geçmek için açıklama satırı yapılan oluşturucuyu değiştirmeniz gerekir.

Not

Bu oluşturucunun çok iş parçacıklı senaryolarda (isThreadSafeiçin true belirterek) nasıl kullanılacağını gösteren kod için Lazy<T>() oluşturucu örneğine bakın.

Örnek, yavaş başlatılacak bir LargeObject sınıfı tanımlar. Main yönteminde örnek bir Lazy<T> örneği oluşturur ve duraklatılır. Enter tuşuna bastığınızda, örnek Lazy<T> örneğin Value özelliğine erişir ve bu da başlatmanın gerçekleşmesine neden olur. LargeObject sınıfının oluşturucusunun bir konsol iletisi görüntülenir.

Not

Kolaylık olması için, bu örnekte Lazy<T>genel bir örneği kullanılır ve tüm yöntemler static (Visual Basic'teShared) kullanılır. Bunlar gecikmeli başlatma kullanımına yönelik gereksinimler değildir.

using System;
using System.Threading;

class Program
{
    static Lazy<LargeObject> lazyLargeObject = null;

    static void Main()
    {
        // The lazy initializer is created here. LargeObject is not created until the
        // ThreadProc method executes.
        lazyLargeObject = new Lazy<LargeObject>(false);

        // The following lines show how to use other constructors to achieve exactly the
        // same result as the previous line:
        //lazyLargeObject = new Lazy<LargeObject>(LazyThreadSafetyMode.None);

        Console.WriteLine(
            "\r\nLargeObject is not created until you access the Value property of the lazy" +
            "\r\ninitializer. Press Enter to create LargeObject.");
        Console.ReadLine();

        LargeObject large = lazyLargeObject.Value;

        large.Data[11] = 89;

        Console.WriteLine("\r\nPress Enter to end the program");
        Console.ReadLine();
    }
}

class LargeObject
{
    public LargeObject()
    {
        Console.WriteLine("LargeObject was created on thread id {0}.",
            Thread.CurrentThread.ManagedThreadId);
    }
    public long[] Data = new long[100000000];
}

/* This example produces output similar to the following:

LargeObject is not created until you access the Value property of the lazy
initializer. Press Enter to create LargeObject.

LargeObject was created on thread id 1.

Press Enter to end the program
 */

open System
open System.Threading

type LargeObject () =
    do
        printfn $"LargeObject was created on thread id {Thread.CurrentThread.ManagedThreadId}."

    member val Data = Array.zeroCreate<int64> 100000000 with get

// The lazy initializer is created here. LargeObject is not created until the
// ThreadProc method executes.
let lazyLargeObject = Lazy<LargeObject> false
// The following lines show how to use other constructors to achieve exactly the
// same result as the previous line:
//     let lazyLargeObject = Lazy<LargeObject>(LazyThreadSafetyMode.None)

printfn """
LargeObject is not created until you access the Value property of the lazy
initializer. Press Enter to create LargeObject."""
stdin.ReadLine() |> ignore

let large = lazyLargeObject.Value

large.Data[11] <- 89

printfn "\nPress Enter to end the program"
stdin.ReadLine() |> ignore


// This example produces output similar to the following:
//     LargeObject is not created until you access the Value property of the lazy
//     initializer. Press Enter to create LargeObject.
//     
//     LargeObject was created on thread id 1.
//     
//     Press Enter to end the program

Imports System.Threading

Friend Class Program
    Private Shared lazyLargeObject As Lazy(Of LargeObject) = Nothing

    Shared Sub Main()
        ' The lazy initializer is created here. LargeObject is not created until the 
        ' ThreadProc method executes.
        lazyLargeObject = New Lazy(Of LargeObject)(False)

        ' The following lines show how to use other constructors to achieve exactly the
        ' same result as the previous line: 
        'lazyLargeObject = new Lazy<LargeObject>(LazyThreadSafetyMode.None);


        Console.WriteLine( _
            vbCrLf & "LargeObject is not created until you access the Value property of the lazy" _
            & vbCrLf & "initializer. Press Enter to create LargeObject.")
        Console.ReadLine()

        Dim large As LargeObject = lazyLargeObject.Value

        large.Data(11) = 89

        Console.WriteLine(vbCrLf & "Press Enter to end the program")
        Console.ReadLine()
    End Sub
End Class

Friend Class LargeObject
    Public Sub New()
        Console.WriteLine("LargeObject was created on thread id {0}.", _
            Thread.CurrentThread.ManagedThreadId)
    End Sub
    Public Data(100000000) As Long
End Class

' This example produces output similar to the following:
'
'LargeObject is not created until you access the Value property of the lazy
'initializer. Press Enter to create LargeObject.
'
'LargeObject was created on thread id 1.
'
'Press Enter to end the program

Açıklamalar

bu oluşturucuyla başlatılan bir Lazy<T> örneğin iş parçacığı güvenlik modu, isThreadSafetrueise LazyThreadSafetyMode.ExecutionAndPublication olur; aksi takdirde, modu LazyThreadSafetyMode.None. İş parçacığı güvenlik modu, birden çok iş parçacığının Lazy<T> örneğini başlatmaya çalışma davranışını açıklar. LazyThreadSafetyMode.PublicationOnly modunu belirtmek için Lazy<T>(Func<T>, LazyThreadSafetyMode) veya Lazy<T>(LazyThreadSafetyMode) oluşturucuyu kullanın.

Bu oluşturucuyla oluşturulan bir Lazy<T> örneği özel durumları önbelleğe almaz. Daha fazla bilgi için Lazy<T> sınıfına veya System.Threading.LazyThreadSafetyMode numaralandırmaya bakın.

Ayrıca bkz.

• Gecikmeli Başlatma

Lazy<T>(Func<T>)

Kaynak:

Lazy.cs

Lazy<T> sınıfının yeni bir örneğini başlatır. Gecikmeli başlatma gerçekleştiğinde, belirtilen başlatma işlevi kullanılır.

public:
 Lazy(Func<T> ^ valueFactory);

public Lazy (Func<T> valueFactory);

new Lazy<'T> : Func<'T> -> Lazy<'T>

Public Sub New (valueFactory As Func(Of T))

Parametreler

valueFactory

Func<T>

Gerektiğinde lazily initialized değerini üretmek için çağrılan temsilci.

Özel durumlar

ArgumentNullException

valueFactory null.

Örnekler

Aşağıdaki örnek, özel durum önbelleğe alma ile yavaş başlatma sağlamak için bu oluşturucunun kullanımını gösterir. Ayrıca Lazy<T>(Func<T>, Boolean) oluşturucunun (isThreadSafeiçin true belirtme) ve Lazy<T>(Func<T>, LazyThreadSafetyMode) oluşturucunun (modeiçin LazyThreadSafetyMode.ExecutionAndPublication belirtme) kullanımını da gösterir. Farklı bir oluşturucuya geçmek için açıklama satırı yapılan oluşturucuları değiştirmeniz gerekir.

Örnek, birkaç iş parçacığından biri tarafından yavaş başlatılacak bir LargeObject sınıfı tanımlar. Kodun üç önemli bölümü başlatıcının oluşturulmasını, gerçek başlatmayı ve özel durum önbelleğe almayı gösteren LargeObject sınıfının oluşturucusunu gösterir. Main yönteminin başında, örnek LargeObjectiçin iş parçacığı güvenli gecikme başlatıcısı oluşturur:

lazyLargeObject = new Lazy<LargeObject>(InitLargeObject);

// The following lines show how to use other constructors to achieve exactly the
// same result as the previous line:
//lazyLargeObject = new Lazy<LargeObject>(InitLargeObject, true);
//lazyLargeObject = new Lazy<LargeObject>(InitLargeObject, LazyThreadSafetyMode.ExecutionAndPublication);

let lazyLargeObject = Lazy<LargeObject> initLargeObject

// The following lines show how to use other constructors to achieve exactly the
// same result as the previous line:
//     let lazyLargeObject = Lazy<LargeObject>(initLargeObject, true)
//     let lazyLargeObject = Lazy<LargeObject>(initLargeObject, LazyThreadSafetyMode.ExecutionAndPublication)

lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject)

' The following lines show how to use other constructors to achieve exactly the
' same result as the previous line: 
'lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject, True)
'lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject, LazyThreadSafetyMode.ExecutionAndPublication)

Örnek üç iş parçacığı oluşturur ve başlatır. Üç iş parçacığı tarafından kullanılan ThreadProc yöntemi, LargeObject örneğini almak için Value özelliğini çağırır:

try
{
    LargeObject large = lazyLargeObject.Value;

    // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
    //            object after creation. You must lock the object before accessing it,
    //            unless the type is thread safe. (LargeObject is not thread safe.)
    lock(large)
    {
        large.Data[0] = Thread.CurrentThread.ManagedThreadId;
        Console.WriteLine("Initialized by thread {0}; last used by thread {1}.",
            large.InitializedBy, large.Data[0]);
    }
}
catch (ApplicationException aex)
{
    Console.WriteLine("Exception: {0}", aex.Message);
}

try
    let large = lazyLargeObject.Value

    // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
    //            object after creation. You must lock the object before accessing it,
    //            unless the type is thread safe. (LargeObject is not thread safe.)
    lock large (fun () -> 
        large.Data[0] <- Thread.CurrentThread.ManagedThreadId
        printfn $"Initialized by thread {large.InitializedBy} last used by thread {large.Data[0]}.")
with :? ApplicationException as aex ->
    printfn $"Exception: {aex.Message}"

Try
    Dim large As LargeObject = lazyLargeObject.Value

    ' IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the  
    '            object after creation. You must lock the object before accessing it,
    '            unless the type is thread safe. (LargeObject is not thread safe.)
    SyncLock large
        large.Data(0) = Thread.CurrentThread.ManagedThreadId
        Console.WriteLine("Initialized by thread {0}; last used by thread {1}.", _
            large.InitializedBy, large.Data(0))
    End SyncLock
Catch aex As ApplicationException
    Console.WriteLine("Exception: {0}", aex.Message)
End Try

LargeObject sınıfının oluşturucusunda kodun üçüncü anahtar bölümü, bir LargeObject örneği ilk kez oluşturulduğunda bir özel durum oluşturur, ancak bundan sonra örnek oluşturmanın gerçekleşmesine izin verir:

static int instanceCount = 0;
public LargeObject()
{
    if (1 == Interlocked.Increment(ref instanceCount))
    {
        throw new ApplicationException("Throw only ONCE.");
    }

    initBy = Thread.CurrentThread.ManagedThreadId;
    Console.WriteLine("LargeObject was created on thread id {0}.", initBy);
}

type LargeObject() =
    static let mutable instanceCount = 0
    let initBy = Thread.CurrentThread.ManagedThreadId
    do
        if 1 = Interlocked.Increment &instanceCount then
            raise (ApplicationException "Throw only ONCE.")
        printfn $"LargeObject was created on thread id {initBy}."

Private Shared instanceCount As Integer = 0
Public Sub New()
    If 1 = Interlocked.Increment(instanceCount) Then
        Throw New ApplicationException("Throw only ONCE.")
    End If

    initBy = Thread.CurrentThread.ManagedThreadId
    Console.WriteLine("LargeObject was created on thread id {0}.", initBy)
End Sub

Örnek çalıştırıldığında, LargeObject örneğini oluşturmaya çalışan ilk iş parçacığı başarısız olur ve özel durum yakalanır. Sonraki iş parçacığının başarıyla bir örnek oluşturmasını bekleyebilirsiniz, ancak Lazy<T> nesnesi özel durumu önbelleğe aldı. Bu nedenle, üç iş parçacığı da özel durum oluşturur.

Not

Kolaylık olması için, bu örnekte Lazy<T>genel bir örneği kullanılır ve tüm yöntemler static (Visual Basic'teShared) kullanılır. Bunlar gecikmeli başlatma kullanımına yönelik gereksinimler değildir.

using System;
using System.Threading;

class Program
{
    static Lazy<LargeObject> lazyLargeObject = null;

    static LargeObject InitLargeObject()
    {
        return new LargeObject();
    }

    static void Main()
    {
        // The lazy initializer is created here. LargeObject is not created until the
        // ThreadProc method executes.
        lazyLargeObject = new Lazy<LargeObject>(InitLargeObject);

        // The following lines show how to use other constructors to achieve exactly the
        // same result as the previous line:
        //lazyLargeObject = new Lazy<LargeObject>(InitLargeObject, true);
        //lazyLargeObject = new Lazy<LargeObject>(InitLargeObject, LazyThreadSafetyMode.ExecutionAndPublication);

        Console.WriteLine(
            "\r\nLargeObject is not created until you access the Value property of the lazy" +
            "\r\ninitializer. Press Enter to create LargeObject.");
        Console.ReadLine();

        // Create and start 3 threads, each of which tries to use LargeObject.
        Thread[] threads = { new Thread(ThreadProc), new Thread(ThreadProc), new Thread(ThreadProc) };
        foreach (Thread t in threads)
        {
            t.Start();
        }

        // Wait for all 3 threads to finish. (The order doesn't matter.)
        foreach (Thread t in threads)
        {
            t.Join();
        }

        Console.WriteLine("\r\nPress Enter to end the program");
        Console.ReadLine();
    }

    static void ThreadProc(object state)
    {
        try
        {
            LargeObject large = lazyLargeObject.Value;

            // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
            //            object after creation. You must lock the object before accessing it,
            //            unless the type is thread safe. (LargeObject is not thread safe.)
            lock(large)
            {
                large.Data[0] = Thread.CurrentThread.ManagedThreadId;
                Console.WriteLine("Initialized by thread {0}; last used by thread {1}.",
                    large.InitializedBy, large.Data[0]);
            }
        }
        catch (ApplicationException aex)
        {
            Console.WriteLine("Exception: {0}", aex.Message);
        }
    }
}

class LargeObject
{
    int initBy = 0;
    public int InitializedBy { get { return initBy; } }

    static int instanceCount = 0;
    public LargeObject()
    {
        if (1 == Interlocked.Increment(ref instanceCount))
        {
            throw new ApplicationException("Throw only ONCE.");
        }

        initBy = Thread.CurrentThread.ManagedThreadId;
        Console.WriteLine("LargeObject was created on thread id {0}.", initBy);
    }
    public long[] Data = new long[100000000];
}

/* This example produces output similar to the following:

LargeObject is not created until you access the Value property of the lazy
initializer. Press Enter to create LargeObject.

Exception: Throw only ONCE.
Exception: Throw only ONCE.
Exception: Throw only ONCE.

Press Enter to end the program
 */

open System
open System.Threading

type LargeObject() =
    static let mutable instanceCount = 0
    let initBy = Thread.CurrentThread.ManagedThreadId
    do
        if 1 = Interlocked.Increment &instanceCount then
            raise (ApplicationException "Throw only ONCE.")
        printfn $"LargeObject was created on thread id {initBy}."
    member _.InitializedBy = initBy
    member val Data = Array.zeroCreate<int64> 100000000

let initLargeObject () =
    LargeObject()

// The lazy initializer is created here. LargeObject is not created until the
// ThreadProc method executes.
let lazyLargeObject = Lazy<LargeObject> initLargeObject

// The following lines show how to use other constructors to achieve exactly the
// same result as the previous line:
//     let lazyLargeObject = Lazy<LargeObject>(initLargeObject, true)
//     let lazyLargeObject = Lazy<LargeObject>(initLargeObject, LazyThreadSafetyMode.ExecutionAndPublication)

let threadProc _ =
    try
        let large = lazyLargeObject.Value

        // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
        //            object after creation. You must lock the object before accessing it,
        //            unless the type is thread safe. (LargeObject is not thread safe.)
        lock large (fun () -> 
            large.Data[0] <- Thread.CurrentThread.ManagedThreadId
            printfn $"Initialized by thread {large.InitializedBy} last used by thread {large.Data[0]}.")
    with :? ApplicationException as aex ->
        printfn $"Exception: {aex.Message}"

printfn """
LargeObject is not created until you access the Value property of the lazy
initializer. Press Enter to create LargeObject."""
stdin.ReadLine () |> ignore

// Create and start 3 threads, each of which tries to use LargeObject.
let threads = 
    [| Thread(ParameterizedThreadStart threadProc); Thread(ParameterizedThreadStart threadProc); Thread(ParameterizedThreadStart threadProc) |]
for t in threads do
    t.Start()

// Wait for all 3 threads to finish. (The order doesn't matter.)
for t in threads do
    t.Join()

printfn "\nPress Enter to end the program"
stdin.ReadLine() |> ignore

// This example produces output similar to the following:
//     LargeObject is not created until you access the Value property of the lazy
//     initializer. Press Enter to create LargeObject.
//     
//     Exception: Throw only ONCE.
//     Exception: Throw only ONCE.
//     Exception: Throw only ONCE.
//     
//     Press Enter to end the program

Imports System.Threading

Friend Class Program
    Private Shared lazyLargeObject As Lazy(Of LargeObject) = Nothing

    Private Shared Function InitLargeObject() As LargeObject
        Return New LargeObject()
    End Function


    Shared Sub Main()
        ' The lazy initializer is created here. LargeObject is not created until the 
        ' ThreadProc method executes.
        lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject)

        ' The following lines show how to use other constructors to achieve exactly the
        ' same result as the previous line: 
        'lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject, True)
        'lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject, LazyThreadSafetyMode.ExecutionAndPublication)


        Console.WriteLine(vbCrLf _
            & "LargeObject is not created until you access the Value property of the lazy" _
            & vbCrLf & "initializer. Press Enter to create LargeObject.")
        Console.ReadLine()

        ' Create and start 3 threads, each of which tries to use LargeObject.
        Dim threads() As Thread = { New Thread(AddressOf ThreadProc), _
            New Thread(AddressOf ThreadProc), New Thread(AddressOf ThreadProc) }
        For Each t As Thread In threads
            t.Start()
        Next t

        ' Wait for all 3 threads to finish. (The order doesn't matter.)
        For Each t As Thread In threads
            t.Join()
        Next t

        Console.WriteLine(vbCrLf & "Press Enter to end the program")
        Console.ReadLine()
    End Sub


    Private Shared Sub ThreadProc(ByVal state As Object)
        Try
            Dim large As LargeObject = lazyLargeObject.Value

            ' IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the  
            '            object after creation. You must lock the object before accessing it,
            '            unless the type is thread safe. (LargeObject is not thread safe.)
            SyncLock large
                large.Data(0) = Thread.CurrentThread.ManagedThreadId
                Console.WriteLine("Initialized by thread {0}; last used by thread {1}.", _
                    large.InitializedBy, large.Data(0))
            End SyncLock
        Catch aex As ApplicationException
            Console.WriteLine("Exception: {0}", aex.Message)
        End Try
    End Sub
End Class

Friend Class LargeObject
    Private initBy As Integer = 0
    Public ReadOnly Property InitializedBy() As Integer
        Get
            Return initBy
        End Get
    End Property

    Private Shared instanceCount As Integer = 0
    Public Sub New()
        If 1 = Interlocked.Increment(instanceCount) Then
            Throw New ApplicationException("Throw only ONCE.")
        End If

        initBy = Thread.CurrentThread.ManagedThreadId
        Console.WriteLine("LargeObject was created on thread id {0}.", initBy)
    End Sub
    Public Data(99999999) As Long
End Class

' This example produces output similar to the following:
'
'LargeObject is not created until you access the Value property of the lazy
'initializer. Press Enter to create LargeObject.
'
'Exception: Throw only ONCE.
'Exception: Throw only ONCE.
'Exception: Throw only ONCE.
'
'Press Enter to end the program
'

Açıklamalar

Bu oluşturucuyla oluşturulan bir örnek birden çok iş parçacığından eşzamanlı olarak kullanılabilir.

Bu oluşturucuyla başlatılan bir Lazy<T> örneğin iş parçacığı güvenlik modu LazyThreadSafetyMode.ExecutionAndPublication. İş parçacığı güvenlik modu, birden çok iş parçacığının Lazy<T> örneğini başlatmaya çalışma davranışını açıklar.

valueFactory tarafından oluşan özel durumlar önbelleğe alınır. Daha fazla bilgi için Lazy<T> sınıfına veya System.Threading.LazyThreadSafetyMode numaralandırmaya bakın.

Ayrıca bkz.

• Gecikmeli Başlatma

Lazy<T>(LazyThreadSafetyMode)

Kaynak:

Lazy.cs

T parametresiz oluşturucuyu ve belirtilen iş parçacığı güvenliği modunu kullanan Lazy<T> sınıfının yeni bir örneğini başlatır.

public:
 Lazy(System::Threading::LazyThreadSafetyMode mode);

public Lazy (System.Threading.LazyThreadSafetyMode mode);

new Lazy<'T> : System.Threading.LazyThreadSafetyMode -> Lazy<'T>

Public Sub New (mode As LazyThreadSafetyMode)

Parametreler

mode

LazyThreadSafetyMode

İş parçacığı güvenlik modunu belirten numaralandırma değerlerinden biri.

Özel durumlar

ArgumentOutOfRangeException

mode geçersiz bir değer içeriyor.

Örnekler

Aşağıdaki örnek, birden çok iş parçacığının bir nesneyi gevşek bir şekilde oluşturmak için yarışmasını sağlayan gecikmeli bir başlatıcı oluşturmak için bu oluşturucunun kullanımını gösterir. Örnek oluşturmada birden çok iş parçacığı başarılı olabilir, ancak tüm iş parçacıkları önce oluşturulan örneği kullanır.

Not

Bu oluşturucunun tek iş parçacıklı senaryolarda (modeiçin LazyThreadSafetyMode.None belirterek) nasıl kullanılacağını gösteren bir örnek için, Lazy<T>(Boolean) oluşturucuya bakın. Çok iş parçacıklı senaryolarda (modeiçin LazyThreadSafetyMode.ExecutionAndPublication belirterek) yarış koşulları yerine kilitleme sağlamak için bu oluşturucunun nasıl kullanılacağını gösteren bir örnek için Lazy<T>() oluşturucuya bakın.

Örnek, birkaç iş parçacığından herhangi biri tarafından yavaş başlatılacak bir LargeObject sınıfı tanımlar. Kodun üç anahtar bölümü başlatıcının oluşturulmasını, gerçek başlatmayı ve LargeObject sınıfının oluşturucu ve sonlandırıcısını gösterir. Main yönteminin başında, örnek LargeObjectyavaş başlatma gerçekleştiren Lazy<T> nesnesini oluşturur:

lazyLargeObject = new Lazy<LargeObject>(LazyThreadSafetyMode.PublicationOnly);

let lazyLargeObject = Lazy<LargeObject> LazyThreadSafetyMode.PublicationOnly

lazyLargeObject = New Lazy(Of LargeObject)(LazyThreadSafetyMode.PublicationOnly)

Örnek, bir ManualResetEvent nesnesi üzerinde blok oluşturan üç iş parçacığı oluşturur ve başlatır, böylece örnek iş parçacıklarını tek seferde serbest bırakabilir. Üç iş parçacığı tarafından kullanılan ThreadProc yönteminde Value özelliğini çağırmak LargeObject örneğini oluşturur:

LargeObject large = lazyLargeObject.Value;

let large = lazyLargeObject.Value

Dim large As LargeObject = lazyLargeObject.Value

Lazy<T> örneğinin oluşturucu LazyThreadSafetyMode.PublicationOnlybelirtildiğinden, üç iş parçacığının da LargeObject örnekleri oluşturmasına izin verilir. Örnek bunu, oluşturucuda ve LargeObject sınıfının sonlandırıcısında konsol iletilerini görüntüleyerek gösterir:

public LargeObject()
{
    initBy = Thread.CurrentThread.ManagedThreadId;
    Console.WriteLine("Constructor: Instance initializing on thread {0}", initBy);
}

~LargeObject()
{
    Console.WriteLine("Finalizer: Instance was initialized on {0}", initBy);
}

type LargeObject() =
    let initBy = Thread.CurrentThread.ManagedThreadId
    do
        printfn $"Constructor: Instance initializing on thread {initBy}"

    override _.Finalize() =
        printfn $"Finalizer: Instance was initialized on {initBy}"

Public Sub New()
    initBy = Thread.CurrentThread.ManagedThreadId
    Console.WriteLine("Constructor: Instance initializing on thread {0}", initBy)
End Sub

Protected Overrides Sub Finalize()
    Console.WriteLine("Finalizer: Instance was initialized on {0}", initBy)
End Sub

Ancak, Lazy<T> nesnesi tüm iş parçacıkları tarafından yalnızca bir örneğin kullanılmasını sağlar. Örnekten elde edilen çıkış, üç iş parçacığının da aynı örneği kullandığını ve ayrıca diğer iki örneğin çöp toplama tarafından geri alınabileceğini gösterir.

Not

Kolaylık olması için, bu örnekte Lazy<T>genel bir örneği kullanılır ve tüm yöntemler static (Visual Basic'teShared) kullanılır. Bunlar gecikmeli başlatma kullanımına yönelik gereksinimler değildir.

using System;
using System.Threading;

class Program
{
    static Lazy<LargeObject> lazyLargeObject = null;

    static void Main()
    {
        // The lazy initializer is created here. LargeObject is not created until the
        // ThreadProc method executes.
        lazyLargeObject = new Lazy<LargeObject>(LazyThreadSafetyMode.PublicationOnly);

        // Create and start 3 threads, passing the same blocking event to all of them.
        ManualResetEvent startingGate = new ManualResetEvent(false);
        Thread[] threads = { new Thread(ThreadProc), new Thread(ThreadProc), new Thread(ThreadProc) };
        foreach (Thread t in threads)
        {
            t.Start(startingGate);
        }

        // Give all 3 threads time to start and wait, then release them all at once.
        Thread.Sleep(50);
        startingGate.Set();

        // Wait for all 3 threads to finish. (The order doesn't matter.)
        foreach (Thread t in threads)
        {
            t.Join();
        }

        Console.WriteLine(
            "\r\nThreads are complete. Running GC.Collect() to reclaim the extra instances.");

        GC.Collect();

        // Allow time for garbage collection, which happens asynchronously.
        Thread.Sleep(100);

        Console.WriteLine(
            "\r\nNote that all three threads used the instance that was not collected.");
        Console.WriteLine("Press Enter to end the program");
        Console.ReadLine();
    }

    static void ThreadProc(object state)
    {
        // Wait for the signal.
        ManualResetEvent waitForStart = (ManualResetEvent) state;
        waitForStart.WaitOne();

        LargeObject large = lazyLargeObject.Value;

        // The following line introduces an artificial delay, to exaggerate the race
        // condition.
        Thread.Sleep(5);

        // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
        //            object after creation. You must lock the object before accessing it,
        //            unless the type is thread safe. (LargeObject is not thread safe.)
        lock(large)
        {
            large.Data[0] = Thread.CurrentThread.ManagedThreadId;
            Console.WriteLine("LargeObject was initialized by thread {0}; last used by thread {1}.",
                large.InitializedBy, large.Data[0]);
        }
    }
}

class LargeObject
{
    int initBy = -1;
    public int InitializedBy { get { return initBy; } }

    public LargeObject()
    {
        initBy = Thread.CurrentThread.ManagedThreadId;
        Console.WriteLine("Constructor: Instance initializing on thread {0}", initBy);
    }

    ~LargeObject()
    {
        Console.WriteLine("Finalizer: Instance was initialized on {0}", initBy);
    }

    public long[] Data = new long[100000000];
}

/* This example produces output similar to the following:

Constructor: Instance initializing on thread 4
Constructor: Instance initializing on thread 3
Constructor: Instance initializing on thread 5
LargeObject was initialized by thread 4; last used by thread 4.
LargeObject was initialized by thread 4; last used by thread 5.
LargeObject was initialized by thread 4; last used by thread 3.

Threads are complete. Running GC.Collect() to reclaim the extra instances.
Finalizer: Instance was initialized on 3
Finalizer: Instance was initialized on 5

Note that all three threads used the instance that was not collected.
Press Enter to end the program

Instance finalizing; initialized on 4
 */

open System
open System.Threading

type LargeObject() =
    let initBy = Thread.CurrentThread.ManagedThreadId
    do
        printfn $"Constructor: Instance initializing on thread {initBy}"

    override _.Finalize() =
        printfn $"Finalizer: Instance was initialized on {initBy}"

    member _.InitializedBy = initBy
    member val Data = Array.zeroCreate<int64> 100000000

// The lazy initializer is created here. LargeObject is not created until the
// ThreadProc method executes.
let lazyLargeObject = Lazy<LargeObject> LazyThreadSafetyMode.PublicationOnly

let threadProc (state: obj) =
    // Wait for the signal.
    let waitForStart = state :?> ManualResetEvent
    waitForStart.WaitOne() |> ignore

    let large = lazyLargeObject.Value

    // The following line introduces an artificial delay, to exaggerate the race
    // condition.
    Thread.Sleep 5

    // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
    //            object after creation. You must lock the object before accessing it,
    //            unless the type is thread safe. (LargeObject is not thread safe.)
    lock large (fun () -> 
        large.Data[0] <- Thread.CurrentThread.ManagedThreadId
        printfn $"LargeObject was initialized by thread {large.InitializedBy} last used by thread {large.Data[0]}.")

// Create and start 3 threads, passing the same blocking event to all of them.
let startingGate = new ManualResetEvent false
let threads = 
    [| Thread(ParameterizedThreadStart threadProc); Thread(ParameterizedThreadStart threadProc); Thread(ParameterizedThreadStart threadProc) |]
for t in threads do
    t.Start startingGate

// Give all 3 threads time to start and wait, then release them all at once.
Thread.Sleep 50
startingGate.Set() |> ignore

// Wait for all 3 threads to finish. (The order doesn't matter.)
for t in threads do
    t.Join()

printfn "\nThreads are complete. Running GC.Collect() to reclaim the extra instances."

GC.Collect()

// Allow time for garbage collection, which happens asynchronously.
Thread.Sleep 100

printfn "\nNote that all three threads used the instance that was not collected."
printfn "Press Enter to end the program"
stdin.ReadLine() |> ignore


// This example produces output similar to the following:
//     Constructor: Instance initializing on thread 4
//     Constructor: Instance initializing on thread 3
//     Constructor: Instance initializing on thread 5
//     LargeObject was initialized by thread 4 last used by thread 4.
//     LargeObject was initialized by thread 4 last used by thread 5.
//     LargeObject was initialized by thread 4 last used by thread 3.
//     
//     Threads are complete. Running GC.Collect() to reclaim the extra instances.
//     Finalizer: Instance was initialized on 3
//     Finalizer: Instance was initialized on 5
//     
//     Note that all three threads used the instance that was not collected.
//     Press Enter to end the program
//     
//     Instance finalizing initialized on 4

Imports System.Threading

Friend Class Program
    Private Shared lazyLargeObject As Lazy(Of LargeObject) = Nothing

    Shared Sub Main()
        ' The lazy initializer is created here. LargeObject is not created until the 
        ' ThreadProc method executes.
        lazyLargeObject = New Lazy(Of LargeObject)(LazyThreadSafetyMode.PublicationOnly)


        ' Create and start 3 threads, passing the same blocking event to all of them.
        Dim startingGate As New ManualResetEvent(False)
        Dim threads() As Thread = { _
            New Thread(AddressOf ThreadProc), _
            New Thread(AddressOf ThreadProc), _
            New Thread(AddressOf ThreadProc) _
        }
        For Each t As Thread In threads
            t.Start(startingGate)
        Next t

        ' Give all 3 threads time to start and wait, then release them all at once.
        Thread.Sleep(50)
        startingGate.Set()

        ' Wait for all 3 threads to finish. (The order doesn't matter.)
        For Each t As Thread In threads
            t.Join()
        Next t

        Console.WriteLine(vbCrLf & _
            "Threads are complete. Running GC.Collect() to reclaim the extra instances.")

        GC.Collect()

        ' Allow time for garbage collection, which happens asynchronously.
        Thread.Sleep(100)

        Console.WriteLine(vbCrLf & _
            "Note that all three threads used the instance that was not collected.")
        Console.WriteLine("Press Enter to end the program")
        Console.ReadLine()

    End Sub


    Private Shared Sub ThreadProc(ByVal state As Object)
        ' Wait for the signal.
        Dim waitForStart As ManualResetEvent = CType(state, ManualResetEvent)
        waitForStart.WaitOne()

        Dim large As LargeObject = lazyLargeObject.Value

        ' The following line introduces an artificial delay to exaggerate the race condition.
        Thread.Sleep(5)

        ' IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the  
        '            object after creation. You must lock the object before accessing it,
        '            unless the type is thread safe. (LargeObject is not thread safe.)
        SyncLock large
            large.Data(0) = Thread.CurrentThread.ManagedThreadId
            Console.WriteLine( _
                "LargeObject was initialized by thread {0}; last used by thread {1}.", _
                large.InitializedBy, large.Data(0))
        End SyncLock
    End Sub
End Class

Friend Class LargeObject
    Private initBy As Integer = -1
    Public ReadOnly Property InitializedBy() As Integer
        Get
            Return initBy
        End Get
    End Property

    Public Sub New()
        initBy = Thread.CurrentThread.ManagedThreadId
        Console.WriteLine("Constructor: Instance initializing on thread {0}", initBy)
    End Sub

    Protected Overrides Sub Finalize()
        Console.WriteLine("Finalizer: Instance was initialized on {0}", initBy)
    End Sub

    Public Data(100000000) As Long
End Class

' This example produces output similar to the following:
'
'Constructor: Instance initializing on thread 3
'Constructor: Instance initializing on thread 5
'Constructor: Instance initializing on thread 4
'LargeObject was initialized by thread 3; last used by thread 4.
'LargeObject was initialized by thread 3; last used by thread 3.
'LargeObject was initialized by thread 3; last used by thread 5.
'
'Threads are complete. Running GC.Collect() to reclaim the extra instances.
'Finalizer: Instance was initialized on 5
'Finalizer: Instance was initialized on 4
'
'Note that all three threads used the instance that was not collected.
'Press Enter to end the program
'
'Finalizer: Instance was initialized on 3
'

Açıklamalar

Lazy<T> örneğin iş parçacığı güvenlik modu, birden çok iş parçacığının Lazy<T> örneğini başlatmaya çalışma davranışını açıklar.

Bu oluşturucuyla oluşturulan bir Lazy<T> örneği özel durumları önbelleğe almaz. Daha fazla bilgi için Lazy<T> sınıfına veya System.Threading.LazyThreadSafetyMode numaralandırmaya bakın.

Ayrıca bkz.

• LazyThreadSafetyMode
• Gecikmeli Başlatma

Lazy<T>(T)

Kaynak:

Lazy.cs

Lazy<T> sınıfının önceden tanımlanmış bir değer kullanan yeni bir örneğini başlatır.

public:
 Lazy(T value);

public Lazy (T value);

new Lazy<'T> : 'T -> Lazy<'T>

Public Sub New (value As T)

Parametreler

value

T

Kullanılacak ön başlatılmamış değer.

Açıklamalar

Bu oluşturucuyla oluşturulan bir örnek birden çok iş parçacığı tarafından eşzamanlı olarak kullanılabilir.

Lazy<T>(Func<T>, Boolean)

Kaynak:

Lazy.cs

Lazy<T> sınıfının yeni bir örneğini başlatır. Gecikmeli başlatma gerçekleştiğinde, belirtilen başlatma işlevi ve başlatma modu kullanılır.

public:
 Lazy(Func<T> ^ valueFactory, bool isThreadSafe);

public Lazy (Func<T> valueFactory, bool isThreadSafe);

new Lazy<'T> : Func<'T> * bool -> Lazy<'T>

Public Sub New (valueFactory As Func(Of T), isThreadSafe As Boolean)

Parametreler

valueFactory

Func<T>

Gerektiğinde lazily initialized değerini üretmek için çağrılan temsilci.

isThreadSafe

Boolean

Bu örneği birden çok iş parçacığı tarafından eşzamanlı olarak kullanılabilir hale getirmek için true; Bu örneği aynı anda yalnızca bir iş parçacığı tarafından kullanılabilir hale getirmek için false.

Özel durumlar

ArgumentNullException

valueFactory null.

Örnekler

Aşağıdaki örnek, tek bir iş parçacığı içeren bir senaryoda özel durum önbelleğe alma ile yavaş başlatma sağlamak için bu oluşturucunun kullanımını gösterir. Ayrıca Lazy<T> oluşturucunun kullanımını da gösterir (modeiçin LazyThreadSafetyMode.None belirtir). Bu oluşturucuya geçmek için açıklama satırı yapılan oluşturucuyu değiştirmeniz gerekir.

Not

Bu oluşturucunun çok iş parçacıklı senaryolarda (isThreadSafeiçin true belirterek) nasıl kullanılacağını gösteren kod için Lazy<T>(Func<T>) oluşturucu örneğine bakın.

Örnek, birkaç iş parçacığından biri tarafından yavaş başlatılacak bir LargeObject sınıfı tanımlar. Kodun üç önemli bölümü başlatıcının oluşturulmasını, gerçek başlatmayı ve özel durum önbelleğe almayı gösteren LargeObject sınıfının oluşturucusunu gösterir. Main yönteminin başında, örnek LargeObjectiçin iş parçacığı güvenli gecikme başlatıcısı oluşturur:

lazyLargeObject = new Lazy<LargeObject>(InitLargeObject, false);

// The following lines show how to use other constructors to achieve exactly the
// same result as the previous line:
//lazyLargeObject = new Lazy<LargeObject>(InitLargeObject, LazyThreadSafetyMode.None);

let lazyLargeObject = Lazy<LargeObject>(initLargeObject, false)

// The following lines show how to use other constructors to achieve exactly the
// same result as the previous line:
//     let lazyLargeObject = Lazy<LargeObject>(initLargeObject, LazyThreadSafetyMode.None)

lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject, False)

' The following lines show how to use other constructors to achieve exactly the
' same result as the previous line: 
'lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject, LazyThreadSafetyMode.None)

Oluşturucuya yapılan çağrıda isThreadSafe parametresi falseolduğundan Lazy<T> iş parçacığı güvenli değildir. İş parçacığı güvenli olmadığından, örnek Value özelliğini aynı iş parçacığında üç kez çağırır:

for (int i = 0; i < 3; i++)
{
    try
    {
        LargeObject large = lazyLargeObject.Value;
        large.Data[11] = 89;
    }
    catch (ApplicationException aex)
    {
        Console.WriteLine("Exception: {0}", aex.Message);
    }
}

for _ = 0 to 2 do
    try
        let large = lazyLargeObject.Value
        large.Data[11] <- 89
    with :? ApplicationException as aex ->
        printfn $"Exception: {aex.Message}"

For i As Integer = 0 To 2
    Try
        Dim large As LargeObject = lazyLargeObject.Value
        large.Data(11) = 89
    Catch aex As ApplicationException
        Console.WriteLine("Exception: {0}", aex.Message)
    End Try
Next i

LargeObject sınıfının oluşturucusunda kodun üçüncü anahtar bölümü, bir LargeObject örneği ilk kez oluşturulduğunda bir özel durum oluşturur, ancak bundan sonra örnek oluşturmanın gerçekleşmesine izin verir:

static bool pleaseThrow = true;
public LargeObject()
{
    if (pleaseThrow)
    {
        pleaseThrow = false;
        throw new ApplicationException("Throw only ONCE.");
    }

    Console.WriteLine("LargeObject was created on thread id {0}.",
        Thread.CurrentThread.ManagedThreadId);
}

type LargeObject() =
    static let mutable pleaseThrow = true
    do
        if pleaseThrow then
            pleaseThrow <- false
            raise (ApplicationException "Throw only ONCE.")
        printfn $"LargeObject was created on thread id {Thread.CurrentThread.ManagedThreadId}."

Private Shared pleaseThrow As Boolean = True
Public Sub New()
    If pleaseThrow Then
        pleaseThrow = False
        Throw New ApplicationException("Throw only ONCE.")
    End If

    Console.WriteLine("LargeObject was created on thread id {0}.", _
        Thread.CurrentThread.ManagedThreadId)
End Sub

Örnek çalıştırıldığında, ilk LargeObject örneği oluşturma girişimi başarısız olur ve özel durum yakalanmış olur. Sonraki denemenin başarılı olmasını bekleyebilirsiniz, ancak Lazy<T> nesnesi özel durumu önbelleğe aldı. Bu nedenle, üç girişim de özel durum oluşturur.

Not

Kolaylık olması için, bu örnekte Lazy<T>genel bir örneği kullanılır ve tüm yöntemler static (Visual Basic'teShared) kullanılır. Bunlar gecikmeli başlatma kullanımına yönelik gereksinimler değildir.

using System;
using System.Threading;

class Program
{
    static Lazy<LargeObject> lazyLargeObject = null;

    static LargeObject InitLargeObject()
    {
        return new LargeObject();
    }

    static void Main()
    {
        // The lazy initializer is created here. LargeObject is not created until the
        // ThreadProc method executes.
        lazyLargeObject = new Lazy<LargeObject>(InitLargeObject, false);

        // The following lines show how to use other constructors to achieve exactly the
        // same result as the previous line:
        //lazyLargeObject = new Lazy<LargeObject>(InitLargeObject, LazyThreadSafetyMode.None);

        Console.WriteLine(
            "\r\nLargeObject is not created until you access the Value property of the lazy" +
            "\r\ninitializer. Press Enter to create LargeObject (three tries).");
        Console.ReadLine();

        for (int i = 0; i < 3; i++)
        {
            try
            {
                LargeObject large = lazyLargeObject.Value;
                large.Data[11] = 89;
            }
            catch (ApplicationException aex)
            {
                Console.WriteLine("Exception: {0}", aex.Message);
            }
        }

        Console.WriteLine("\r\nPress Enter to end the program");
        Console.ReadLine();
    }
}

class LargeObject
{
    static bool pleaseThrow = true;
    public LargeObject()
    {
        if (pleaseThrow)
        {
            pleaseThrow = false;
            throw new ApplicationException("Throw only ONCE.");
        }

        Console.WriteLine("LargeObject was created on thread id {0}.",
            Thread.CurrentThread.ManagedThreadId);
    }
    public long[] Data = new long[100000000];
}

/* This example produces output similar to the following:

LargeObject is not created until you access the Value property of the lazy
initializer. Press Enter to create LargeObject (three tries).

Exception: Throw only ONCE.
Exception: Throw only ONCE.
Exception: Throw only ONCE.

Press Enter to end the program
 */

open System
open System.Threading

type LargeObject() =
    static let mutable pleaseThrow = true
    do
        if pleaseThrow then
            pleaseThrow <- false
            raise (ApplicationException "Throw only ONCE.")
        printfn $"LargeObject was created on thread id {Thread.CurrentThread.ManagedThreadId}."
    member val Data = Array.zeroCreate<int64> 100000000

let initLargeObject () =
    LargeObject()

// The lazy initializer is created here. LargeObject is not created until the
// ThreadProc method executes.
let lazyLargeObject = Lazy<LargeObject>(initLargeObject, false)

// The following lines show how to use other constructors to achieve exactly the
// same result as the previous line:
//     let lazyLargeObject = Lazy<LargeObject>(initLargeObject, LazyThreadSafetyMode.None)

printfn """
LargeObject is not created until you access the Value property of the lazy
initializer. Press Enter to create LargeObject (three tries)."""
stdin.ReadLine() |> ignore

for _ = 0 to 2 do
    try
        let large = lazyLargeObject.Value
        large.Data[11] <- 89
    with :? ApplicationException as aex ->
        printfn $"Exception: {aex.Message}"

printfn "\nPress Enter to end the program"
stdin.ReadLine() |> ignore

// This example produces output similar to the following:
//     LargeObject is not created until you access the Value property of the lazy
//     initializer. Press Enter to create LargeObject (three tries).
//     
//     Exception: Throw only ONCE.
//     Exception: Throw only ONCE.
//     Exception: Throw only ONCE.
//     
//     Press Enter to end the program

Imports System.Threading

Friend Class Program
    Private Shared lazyLargeObject As Lazy(Of LargeObject) = Nothing

    Private Shared Function InitLargeObject() As LargeObject
        Return New LargeObject()
    End Function


    Shared Sub Main()
        ' The lazy initializer is created here. LargeObject is not created until the 
        ' ThreadProc method executes.
        lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject, False)

        ' The following lines show how to use other constructors to achieve exactly the
        ' same result as the previous line: 
        'lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject, LazyThreadSafetyMode.None)


        Console.WriteLine(vbCrLf _
            & "LargeObject is not created until you access the Value property of the lazy" _
            & vbCrLf & "initializer. Press Enter to create LargeObject (three tries).")
        Console.ReadLine()

        For i As Integer = 0 To 2
            Try
                Dim large As LargeObject = lazyLargeObject.Value
                large.Data(11) = 89
            Catch aex As ApplicationException
                Console.WriteLine("Exception: {0}", aex.Message)
            End Try
        Next i

        Console.WriteLine(vbCrLf & "Press Enter to end the program")
        Console.ReadLine()
    End Sub
End Class

Friend Class LargeObject
    Private Shared pleaseThrow As Boolean = True
    Public Sub New()
        If pleaseThrow Then
            pleaseThrow = False
            Throw New ApplicationException("Throw only ONCE.")
        End If

        Console.WriteLine("LargeObject was created on thread id {0}.", _
            Thread.CurrentThread.ManagedThreadId)
    End Sub
    Public Data(100000000) As Long
End Class

' This example produces output similar to the following:
'
'LargeObject is not created until you access the Value property of the lazy
'initializer. Press Enter to create LargeObject (three tries).
'
'Exception: Throw only ONCE.
'Exception: Throw only ONCE.
'Exception: Throw only ONCE.
'
'Press Enter to end the program
'

Açıklamalar

bu oluşturucuyla başlatılan bir Lazy<T> örneğin iş parçacığı güvenlik modu, isThreadSafetrueise LazyThreadSafetyMode.ExecutionAndPublication olur; aksi takdirde, modu LazyThreadSafetyMode.None. İş parçacığı güvenlik modu, birden çok iş parçacığının Lazy<T> örneğini başlatmaya çalışma davranışını açıklar.

LazyThreadSafetyMode.PublicationOnly modunu belirtmek için Lazy<T>(Func<T>, LazyThreadSafetyMode) veya Lazy<T>(LazyThreadSafetyMode) oluşturucuyu kullanın.

valueFactory tarafından oluşan özel durumlar önbelleğe alınır. Daha fazla bilgi için Lazy<T> sınıfına veya System.Threading.LazyThreadSafetyMode numaralandırmaya bakın.

Ayrıca bkz.

• Gecikmeli Başlatma

Lazy<T>(Func<T>, LazyThreadSafetyMode)

Kaynak:

Lazy.cs

Belirtilen başlatma işlevini ve iş parçacığı güvenliği modunu kullanan Lazy<T> sınıfının yeni bir örneğini başlatır.

public:
 Lazy(Func<T> ^ valueFactory, System::Threading::LazyThreadSafetyMode mode);

public Lazy (Func<T> valueFactory, System.Threading.LazyThreadSafetyMode mode);

new Lazy<'T> : Func<'T> * System.Threading.LazyThreadSafetyMode -> Lazy<'T>

Public Sub New (valueFactory As Func(Of T), mode As LazyThreadSafetyMode)

Parametreler

valueFactory

Func<T>

Gerektiğinde lazily initialized değerini üretmek için çağrılan temsilci.

mode

LazyThreadSafetyMode

İş parçacığı güvenlik modunu belirten numaralandırma değerlerinden biri.

Özel durumlar

ArgumentOutOfRangeException

mode geçersiz bir değer içeriyor.

ArgumentNullException

valueFactory null.

Örnekler

Aşağıdaki örnek, birden çok iş parçacığının bir nesneyi gevşek bir şekilde oluşturmak için yarışmasını sağlayan gecikmeli bir başlatıcı oluşturmak için bu oluşturucunun kullanımını gösterir. Örnek oluşturmada birden çok iş parçacığı başarılı olabilir, ancak tüm iş parçacıkları önce oluşturulan örneği kullanır. Buna ek olarak, örnek LazyThreadSafetyMode.PublicationOnlybelirttiğinizde özel durumların hiçbir zaman önbelleğe alınmadığını gösterir. Başlatma işlemi, lazily oluşturulan türün parametresiz oluşturucu tarafından yerine bir işlev tarafından gerçekleştirilse bile.

Not

Bu oluşturucunun tek iş parçacıklı senaryolarda (modeiçin LazyThreadSafetyMode.None belirterek) nasıl kullanılacağını gösteren bir örnek için, Lazy<T>(Boolean) oluşturucuya bakın. Çok iş parçacıklı senaryolarda (modeiçin LazyThreadSafetyMode.ExecutionAndPublication belirterek) yarış koşulları yerine kilitleme sağlamak için bu oluşturucunun nasıl kullanılacağını gösteren bir örnek için Lazy<T>() oluşturucuya bakın.

Örnek, birkaç iş parçacığından herhangi biri tarafından yavaş başlatılacak bir LargeObject sınıfı tanımlar. Kodun dört anahtar bölümü başlatıcının oluşturulmasını, gerçek başlatmayı, başlatma işlevini ve LargeObject sınıfının oluşturucu ve sonlandırıcısını gösterir. Main yönteminin başında, örnek LargeObjectyavaş başlatma gerçekleştiren Lazy<T> nesnesini oluşturur:

lazyLargeObject = new Lazy<LargeObject>(InitLargeObject,
                             LazyThreadSafetyMode.PublicationOnly);

let lazyLargeObject = Lazy<LargeObject>(initLargeObject, LazyThreadSafetyMode.PublicationOnly)

lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject, _
     LazyThreadSafetyMode.PublicationOnly)

Yavaş başlatıcı başlatmayı gerçekleştirmek için bir işlev kullanır. Bu durumda, LargeObject sınıfı için parametresiz oluşturucu olmadığından bir işlev gereklidir.

Örnek, bir ManualResetEvent nesnesi üzerinde blok oluşturan üç iş parçacığı oluşturur ve başlatır, böylece örnek iş parçacıklarını tek seferde serbest bırakabilir. Üç iş parçacığı tarafından kullanılan ThreadProc yönteminde Value özelliğini çağırmak LargeObject örneğini oluşturur:

LargeObject large = null;
try
{
    large = lazyLargeObject.Value;

    // The following line introduces an artificial delay to exaggerate the race condition.
    Thread.Sleep(5);

    // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
    //            object after creation. You must lock the object before accessing it,
    //            unless the type is thread safe. (LargeObject is not thread safe.)
    lock(large)
    {
        large.Data[0] = Thread.CurrentThread.ManagedThreadId;
        Console.WriteLine("LargeObject was initialized by thread {0}; last used by thread {1}.",
            large.InitializedBy, large.Data[0]);
    }
}
catch (ApplicationException ex)
{
    Console.WriteLine("ApplicationException: {0}", ex.Message);
}

try
    let large = lazyLargeObject.Value

    // The following line introduces an artificial delay to exaggerate the race condition.
    Thread.Sleep 5

    // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
    //            object after creation. You must lock the object before accessing it,
    //            unless the type is thread safe. (LargeObject is not thread safe.)
    lock large (fun () -> 
        large.Data[0] <- Thread.CurrentThread.ManagedThreadId
        printfn $"LargeObject was initialized by thread {large.InitializedBy} last used by thread {large.Data[0]}.")
with :? ApplicationException as ex ->
    printfn $"ApplicationException: {ex.Message}"

Dim large As LargeObject = Nothing
Try
    large = lazyLargeObject.Value

    ' The following line introduces an artificial delay to exaggerate the race condition.
    Thread.Sleep(5)

    ' IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the  
    '            object after creation. You must lock the object before accessing it,
    '            unless the type is thread safe. (LargeObject is not thread safe.)
    SyncLock large
        large.Data(0) = Thread.CurrentThread.ManagedThreadId
        Console.WriteLine( _
            "LargeObject was initialized by thread {0}; last used by thread {1}.", _
            large.InitializedBy, large.Data(0))
    End SyncLock
Catch ex As ApplicationException
    Console.WriteLine("ApplicationException: {0}", ex.Message)
End Try

Kodun üçüncü anahtar bölümünde, LargeObject örneğini oluşturmak için gecikmeli başlatma işlevi çağrılır. İşlev, ilk kez çağrıldığında bir özel durum oluşturur:

static int instanceCount = 0;
static LargeObject InitLargeObject()
{
    if (1 == Interlocked.Increment(ref instanceCount))
    {
        throw new ApplicationException(
            String.Format("Lazy initialization function failed on thread {0}.",
            Thread.CurrentThread.ManagedThreadId));
    }
    return new LargeObject(Thread.CurrentThread.ManagedThreadId);
}

let mutable instanceCount = 0
let initLargeObject () =
    if 1 = Interlocked.Increment &instanceCount then
        raise (ApplicationException $"Lazy initialization function failed on thread {Thread.CurrentThread.ManagedThreadId}.")
    LargeObject Thread.CurrentThread.ManagedThreadId

Private Shared instanceCount As Integer = 0
Private Shared Function InitLargeObject() As LargeObject
    If 1 = Interlocked.Increment(instanceCount) Then
        Throw New ApplicationException( _
            "Lazy initialization function failed on thread " & _
            Thread.CurrentThread.ManagedThreadId & ".")
    End If
    Return New LargeObject(Thread.CurrentThread.ManagedThreadId)
End Function

Diğer tüm LazyThreadSafetyMode ayarlarıyla, başlatma işlevindeki işlenmeyen bir özel durum önbelleğe alınır. Ancak LazyThreadSafetyMode.PublicationOnly özel durum önbelleğe almayı engeller. Örnekten alınan çıkış, nesneyi başlatmaya yönelik sonraki bir girişimin başarılı olduğunu gösterir.

Not

Özel durum iletisi genellikle diğer iş parçacıklarının nesneyi başarıyla başlattığını belirten iletilerden sonra görüntülenir. Bunun nedeni, özel durum oluşturma ve yakalama ile ortaya çıkabilecek gecikmedir.

Lazy<T> örneğinin oluşturucu LazyThreadSafetyMode.PublicationOnlybelirtildiğinden, üç iş parçacığının da LargeObject örnekleri oluşturmasına izin verilir. Örnek bunu, oluşturucuda ve LargeObject sınıfının sonlandırıcısında konsol iletilerini görüntüleyerek gösterir:

public LargeObject(int initializedBy)
{
    initBy = initializedBy;
    Console.WriteLine("Constructor: Instance initializing on thread {0}", initBy);
}

~LargeObject()
{
    Console.WriteLine("Finalizer: Instance was initialized on {0}", initBy);
}

type LargeObject(initBy) =
    do
        printfn $"Constructor: Instance initializing on thread {initBy}"

    override _.Finalize() =
        printfn $"Finalizer: Instance was initialized on {initBy}"

Public Sub New(ByVal initializedBy As Integer)
    initBy = initializedBy
    Console.WriteLine("Constructor: Instance initializing on thread {0}", initBy)
End Sub

Protected Overrides Sub Finalize()
    Console.WriteLine("Finalizer: Instance was initialized on {0}", initBy)
End Sub

Lazy<T> nesnesi, tüm iş parçacıkları tarafından yalnızca bir örneğin kullanılmasını sağlar (başlatma işlevinin özel durum oluşturduğu iş parçacığı dışında). Örnekteki çıkışta bu gösterilir.

Not

Kolaylık olması için, bu örnekte Lazy<T>genel bir örneği kullanılır ve tüm yöntemler static (Visual Basic'teShared) kullanılır. Bunlar gecikmeli başlatma kullanımına yönelik gereksinimler değildir.

using System;
using System.Threading;

class Program
{
    static Lazy<LargeObject> lazyLargeObject = null;

    // Factory function for lazy initialization.
    static int instanceCount = 0;
    static LargeObject InitLargeObject()
    {
        if (1 == Interlocked.Increment(ref instanceCount))
        {
            throw new ApplicationException(
                String.Format("Lazy initialization function failed on thread {0}.",
                Thread.CurrentThread.ManagedThreadId));
        }
        return new LargeObject(Thread.CurrentThread.ManagedThreadId);
    }

    static void Main()
    {
        // The lazy initializer is created here. LargeObject is not created until the
        // ThreadProc method executes.
        lazyLargeObject = new Lazy<LargeObject>(InitLargeObject,
                                     LazyThreadSafetyMode.PublicationOnly);

        // Create and start 3 threads, passing the same blocking event to all of them.
        ManualResetEvent startingGate = new ManualResetEvent(false);
        Thread[] threads = { new Thread(ThreadProc), new Thread(ThreadProc), new Thread(ThreadProc) };
        foreach (Thread t in threads)
        {
            t.Start(startingGate);
        }

        // Give all 3 threads time to start and wait, then release them all at once.
        Thread.Sleep(50);
        startingGate.Set();

        // Wait for all 3 threads to finish. (The order doesn't matter.)
        foreach (Thread t in threads)
        {
            t.Join();
        }

        Console.WriteLine(
            "\r\nThreads are complete. Running GC.Collect() to reclaim extra instances.");

        GC.Collect();

        // Allow time for garbage collection, which happens asynchronously.
        Thread.Sleep(100);

        Console.WriteLine("\r\nNote that only one instance of LargeObject was used.");
        Console.WriteLine("Press Enter to end the program");
        Console.ReadLine();
    }

    static void ThreadProc(object state)
    {
        // Wait for the signal.
        ManualResetEvent waitForStart = (ManualResetEvent) state;
        waitForStart.WaitOne();

        LargeObject large = null;
        try
        {
            large = lazyLargeObject.Value;

            // The following line introduces an artificial delay to exaggerate the race condition.
            Thread.Sleep(5);

            // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
            //            object after creation. You must lock the object before accessing it,
            //            unless the type is thread safe. (LargeObject is not thread safe.)
            lock(large)
            {
                large.Data[0] = Thread.CurrentThread.ManagedThreadId;
                Console.WriteLine("LargeObject was initialized by thread {0}; last used by thread {1}.",
                    large.InitializedBy, large.Data[0]);
            }
        }
        catch (ApplicationException ex)
        {
            Console.WriteLine("ApplicationException: {0}", ex.Message);
        }
    }
}

class LargeObject
{
    int initBy = -1;
    public int InitializedBy { get { return initBy; } }

    public LargeObject(int initializedBy)
    {
        initBy = initializedBy;
        Console.WriteLine("Constructor: Instance initializing on thread {0}", initBy);
    }

    ~LargeObject()
    {
        Console.WriteLine("Finalizer: Instance was initialized on {0}", initBy);
    }

    public long[] Data = new long[100000000];
}

/* This example produces output similar to the following:

Constructor: Instance initializing on thread 5
Constructor: Instance initializing on thread 4
ApplicationException: Lazy initialization function failed on thread 3.
LargeObject was initialized by thread 5; last used by thread 5.
LargeObject was initialized by thread 5; last used by thread 4.

Threads are complete. Running GC.Collect() to reclaim extra instances.
Finalizer: Instance was initialized on 4

Note that only one instance of LargeObject was used.
Press Enter to end the program

Finalizer: Instance was initialized on 5
 */

open System
open System.Threading

type LargeObject(initBy) =
    do
        printfn $"Constructor: Instance initializing on thread {initBy}"

    override _.Finalize() =
        printfn $"Finalizer: Instance was initialized on {initBy}"
    member _.InitializedBy = initBy
    member val Data = Array.zeroCreate<int64> 100000000 with get

// Factory function for lazy initialization.
let mutable instanceCount = 0
let initLargeObject () =
    if 1 = Interlocked.Increment &instanceCount then
        raise (ApplicationException $"Lazy initialization function failed on thread {Thread.CurrentThread.ManagedThreadId}.")
    LargeObject Thread.CurrentThread.ManagedThreadId

// The lazy initializer is created here. LargeObject is not created until the
// ThreadProc method executes.
let lazyLargeObject = Lazy<LargeObject>(initLargeObject, LazyThreadSafetyMode.PublicationOnly)

let threadProc (state: obj) =
    // Wait for the signal.
    let waitForStart = state :?> ManualResetEvent
    waitForStart.WaitOne() |> ignore

    try
        let large = lazyLargeObject.Value

        // The following line introduces an artificial delay to exaggerate the race condition.
        Thread.Sleep 5

        // IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the
        //            object after creation. You must lock the object before accessing it,
        //            unless the type is thread safe. (LargeObject is not thread safe.)
        lock large (fun () -> 
            large.Data[0] <- Thread.CurrentThread.ManagedThreadId
            printfn $"LargeObject was initialized by thread {large.InitializedBy} last used by thread {large.Data[0]}.")
    with :? ApplicationException as ex ->
        printfn $"ApplicationException: {ex.Message}"

// Create and start 3 threads, passing the same blocking event to all of them.
let startingGate = new ManualResetEvent false
let threads = 
    [| Thread(ParameterizedThreadStart threadProc); Thread(ParameterizedThreadStart threadProc); Thread(ParameterizedThreadStart threadProc) |]
for t in threads do
    t.Start startingGate

// Give all 3 threads time to start and wait, then release them all at once.
Thread.Sleep 50
startingGate.Set() |> ignore

// Wait for all 3 threads to finish. (The order doesn't matter.)
for t in threads do
    t.Join()

printfn "\nThreads are complete. Running GC.Collect() to reclaim extra instances."

GC.Collect()

// Allow time for garbage collection, which happens asynchronously.
Thread.Sleep 100

printfn "\nNote that only one instance of LargeObject was used."
printfn "Press Enter to end the program"
stdin.ReadLine() |> ignore

// This example produces output similar to the following:
//     Constructor: Instance initializing on thread 5
//     Constructor: Instance initializing on thread 4
//     ApplicationException: Lazy initialization function failed on thread 3.
//     LargeObject was initialized by thread 5 last used by thread 5.
//     LargeObject was initialized by thread 5 last used by thread 4.
//     
//     Threads are complete. Running GC.Collect() to reclaim extra instances.
//     Finalizer: Instance was initialized on 4
//     
//     Note that only one instance of LargeObject was used.
//     Press Enter to end the program
//     
//     Finalizer: Instance was initialized on 5

Imports System.Threading

Friend Class Program
    Private Shared lazyLargeObject As Lazy(Of LargeObject) = Nothing

    ' Factory function for lazy initialization.
    Private Shared instanceCount As Integer = 0
    Private Shared Function InitLargeObject() As LargeObject
        If 1 = Interlocked.Increment(instanceCount) Then
            Throw New ApplicationException( _
                "Lazy initialization function failed on thread " & _
                Thread.CurrentThread.ManagedThreadId & ".")
        End If
        Return New LargeObject(Thread.CurrentThread.ManagedThreadId)
    End Function

    Shared Sub Main()
        ' The lazy initializer is created here. LargeObject is not created until the 
        ' ThreadProc method executes.
        lazyLargeObject = New Lazy(Of LargeObject)(AddressOf InitLargeObject, _
             LazyThreadSafetyMode.PublicationOnly)


        ' Create and start 3 threads, passing the same blocking event to all of them.
        Dim startingGate As New ManualResetEvent(False)
        Dim threads() As Thread = { _
            New Thread(AddressOf ThreadProc), _
            New Thread(AddressOf ThreadProc), _
            New Thread(AddressOf ThreadProc) _
        }
        For Each t As Thread In threads
            t.Start(startingGate)
        Next t

        ' Give all 3 threads time to start and wait, then release them all at once.
        Thread.Sleep(50)
        startingGate.Set()

        ' Wait for all 3 threads to finish. (The order doesn't matter.)
        For Each t As Thread In threads
            t.Join()
        Next t

        Console.WriteLine(vbCrLf & _
            "Threads are complete. Running GC.Collect() to reclaim extra instances.")

        GC.Collect()

        ' Allow time for garbage collection, which happens asynchronously.
        Thread.Sleep(100)

        Console.WriteLine(vbCrLf & "Note that only one instance of LargeObject was used.")
        Console.WriteLine("Press Enter to end the program")
        Console.ReadLine()
    End Sub


    Private Shared Sub ThreadProc(ByVal state As Object)
        ' Wait for the signal.
        Dim waitForStart As ManualResetEvent = CType(state, ManualResetEvent)
        waitForStart.WaitOne()

        Dim large As LargeObject = Nothing
        Try
            large = lazyLargeObject.Value

            ' The following line introduces an artificial delay to exaggerate the race condition.
            Thread.Sleep(5)

            ' IMPORTANT: Lazy initialization is thread-safe, but it doesn't protect the  
            '            object after creation. You must lock the object before accessing it,
            '            unless the type is thread safe. (LargeObject is not thread safe.)
            SyncLock large
                large.Data(0) = Thread.CurrentThread.ManagedThreadId
                Console.WriteLine( _
                    "LargeObject was initialized by thread {0}; last used by thread {1}.", _
                    large.InitializedBy, large.Data(0))
            End SyncLock
        Catch ex As ApplicationException
            Console.WriteLine("ApplicationException: {0}", ex.Message)
        End Try
    End Sub
End Class

Friend Class LargeObject
    Private initBy As Integer = -1
    Public ReadOnly Property InitializedBy() As Integer
        Get
            Return initBy
        End Get
    End Property

    Public Sub New(ByVal initializedBy As Integer)
        initBy = initializedBy
        Console.WriteLine("Constructor: Instance initializing on thread {0}", initBy)
    End Sub

    Protected Overrides Sub Finalize()
        Console.WriteLine("Finalizer: Instance was initialized on {0}", initBy)
    End Sub

    Public Data(99999999) As Long
End Class

' This example produces output similar to the following:
'
'Constructor: Instance initializing on thread 4
'ApplicationException: Lazy initialization function failed on thread 3.
'Constructor: Instance initializing on thread 5
'LargeObject was initialized by thread 4; last used by thread 4.
'LargeObject was initialized by thread 4; last used by thread 5.
'
'Threads are complete. Running GC.Collect() to reclaim extra instances.
'Finalizer: Instance was initialized on 5
'
'Note that only one instance of LargeObject was used.
'Press Enter to end the program
'
'Finalizer: Instance was initialized on 4
'

Açıklamalar

Lazy<T> örneğin iş parçacığı güvenlik modu, birden çok iş parçacığının Lazy<T> örneğini başlatmaya çalışma davranışını açıklar.

mode LazyThreadSafetyMode.PublicationOnlyolmadığı sürece, valueFactory tarafından oluşan özel durumlar önbelleğe alınır. Daha fazla bilgi için Lazy<T> sınıfına veya System.Threading.LazyThreadSafetyMode numaralandırmaya bakın.

Ayrıca bkz.

• Gecikmeli Başlatma