Semaphore 建構函式

參考

定義

命名空間:: System.Threading

組件:: System.Threading.dll

組件:: System.dll

組件:: netstandard.dll

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

初始化 Semaphore 類別的新執行個體。

多載

Semaphore(Int32, Int32)	初始化 Semaphore 類別的新執行個體，以及指定並行項目的最大數目及選擇性地保留某些項目。
Semaphore(Int32, Int32, String)	初始化 Semaphore 類別的新執行個體，然後指定初始項目數目與並行項目的最大數目，以及選擇性地指定系統旗號物件的名稱。
Semaphore(Int32, Int32, String, Boolean)	初始化 Semaphore 類別的新執行個體，然後指定初始項目物件數目與並行項目的最大數目，選擇性地指定系統號誌物件的名稱，以及指定接收值的變數，指出是否已建立新的系統號誌。
Semaphore(Int32, Int32, String, Boolean, SemaphoreSecurity)	初始化 Semaphore 類別的新執行個體，然後指定初始項目數目與並行項目的最大數目，選擇性地指定系統號誌物件的名稱，指定接收值的變數 (以指示是否已建立新的系統號誌)，以及指定系統號誌的安全性存取控制。

Semaphore(Int32, Int32)

Source:: Semaphore.cs

Source:: Semaphore.cs

Source:: Semaphore.cs

初始化 Semaphore 類別的新執行個體，以及指定並行項目的最大數目及選擇性地保留某些項目。

public:
 Semaphore(int initialCount, int maximumCount);

public Semaphore (int initialCount, int maximumCount);

new System.Threading.Semaphore : int * int -> System.Threading.Semaphore

Public Sub New (initialCount As Integer, maximumCount As Integer)

參數

initialCount: Int32

可同時授與給號誌的初始要求數目。

maximumCount: Int32

可以同時授與之號誌要求的最大數目。

例外狀況

ArgumentException

initialCount 大於 maximumCount。

ArgumentOutOfRangeException

maximumCount 小於 1。

-或-

initialCount 小於 0。

範例

下列範例會建立最大計數為 3 且初始計數為零的號志。此範例會啟動五個執行緒，這會封鎖等候號志。主執行緒會 Release(Int32) 使用方法多載，將號志計數增加到其最大值，讓三個執行緒進入號志。每個執行緒都會 Thread.Sleep 使用方法來等候一秒，以模擬工作，然後呼叫 Release() 方法多載以釋放旗號。每次放開號志時，就會顯示先前的號志計數。主控台訊息會追蹤號志使用。模擬的時間間隔會針對每個執行緒稍微增加，讓輸出更容易閱讀。

#using <System.dll>
using namespace System;
using namespace System::Threading;

public ref class Example
{
private:
   // A semaphore that simulates a limited resource pool.
   //
   static Semaphore^ _pool;

   // A padding interval to make the output more orderly.
   static int _padding;

public:
   static void Main()
   {
      // Create a semaphore that can satisfy up to three
      // concurrent requests. Use an initial count of zero,
      // so that the entire semaphore count is initially
      // owned by the main program thread.
      //
      _pool = gcnew Semaphore( 0,3 );
      
      // Create and start five numbered threads.
      //
      for ( int i = 1; i <= 5; i++ )
      {
         Thread^ t = gcnew Thread(
            gcnew ParameterizedThreadStart( Worker ) );
         
         // Start the thread, passing the number.
         //
         t->Start( i );
      }
      
      // Wait for half a second, to allow all the
      // threads to start and to block on the semaphore.
      //
      Thread::Sleep( 500 );
      
      // The main thread starts out holding the entire
      // semaphore count. Calling Release(3) brings the
      // semaphore count back to its maximum value, and
      // allows the waiting threads to enter the semaphore,
      // up to three at a time.
      //
      Console::WriteLine( L"Main thread calls Release(3)." );
      _pool->Release( 3 );

      Console::WriteLine( L"Main thread exits." );
   }

private:
   static void Worker( Object^ num )
   {
      // Each worker thread begins by requesting the
      // semaphore.
      Console::WriteLine( L"Thread {0} begins and waits for the semaphore.", num );
      _pool->WaitOne();
      
      // A padding interval to make the output more orderly.
      int padding = Interlocked::Add( _padding, 100 );

      Console::WriteLine( L"Thread {0} enters the semaphore.", num );
      
      // The thread's "work" consists of sleeping for
      // about a second. Each thread "works" a little
      // longer, just to make the output more orderly.
      //
      Thread::Sleep( 1000 + padding );

      Console::WriteLine( L"Thread {0} releases the semaphore.", num );
      Console::WriteLine( L"Thread {0} previous semaphore count: {1}",
         num, _pool->Release() );
   }
};

using System;
using System.Threading;

public class Example
{
    // A semaphore that simulates a limited resource pool.
    //
    private static Semaphore _pool;

    // A padding interval to make the output more orderly.
    private static int _padding;

    public static void Main()
    {
        // Create a semaphore that can satisfy up to three
        // concurrent requests. Use an initial count of zero,
        // so that the entire semaphore count is initially
        // owned by the main program thread.
        //
        _pool = new Semaphore(initialCount: 0, maximumCount: 3);

        // Create and start five numbered threads. 
        //
        for(int i = 1; i <= 5; i++)
        {
            Thread t = new Thread(new ParameterizedThreadStart(Worker));

            // Start the thread, passing the number.
            //
            t.Start(i);
        }

        // Wait for half a second, to allow all the
        // threads to start and to block on the semaphore.
        //
        Thread.Sleep(500);

        // The main thread starts out holding the entire
        // semaphore count. Calling Release(3) brings the 
        // semaphore count back to its maximum value, and
        // allows the waiting threads to enter the semaphore,
        // up to three at a time.
        //
        Console.WriteLine("Main thread calls Release(3).");
        _pool.Release(releaseCount: 3);

        Console.WriteLine("Main thread exits.");
    }

    private static void Worker(object num)
    {
        // Each worker thread begins by requesting the
        // semaphore.
        Console.WriteLine("Thread {0} begins " +
            "and waits for the semaphore.", num);
        _pool.WaitOne();

        // A padding interval to make the output more orderly.
        int padding = Interlocked.Add(ref _padding, 100);

        Console.WriteLine("Thread {0} enters the semaphore.", num);
        
        // The thread's "work" consists of sleeping for 
        // about a second. Each thread "works" a little 
        // longer, just to make the output more orderly.
        //
        Thread.Sleep(1000 + padding);

        Console.WriteLine("Thread {0} releases the semaphore.", num);
        Console.WriteLine("Thread {0} previous semaphore count: {1}",
            num, _pool.Release());
    }
}

Imports System.Threading

Public Class Example

    ' A semaphore that simulates a limited resource pool.
    '
    Private Shared _pool As Semaphore

    ' A padding interval to make the output more orderly.
    Private Shared _padding As Integer

    <MTAThread> _
    Public Shared Sub Main()
        ' Create a semaphore that can satisfy up to three
        ' concurrent requests. Use an initial count of zero,
        ' so that the entire semaphore count is initially
        ' owned by the main program thread.
        '
        _pool = New Semaphore(0, 3)

        ' Create and start five numbered threads. 
        '
        For i As Integer = 1 To 5
            Dim t As New Thread(New ParameterizedThreadStart(AddressOf Worker))
            'Dim t As New Thread(AddressOf Worker)

            ' Start the thread, passing the number.
            '
            t.Start(i)
        Next i

        ' Wait for half a second, to allow all the
        ' threads to start and to block on the semaphore.
        '
        Thread.Sleep(500)

        ' The main thread starts out holding the entire
        ' semaphore count. Calling Release(3) brings the 
        ' semaphore count back to its maximum value, and
        ' allows the waiting threads to enter the semaphore,
        ' up to three at a time.
        '
        Console.WriteLine("Main thread calls Release(3).")
        _pool.Release(3)

        Console.WriteLine("Main thread exits.")
    End Sub

    Private Shared Sub Worker(ByVal num As Object)
        ' Each worker thread begins by requesting the
        ' semaphore.
        Console.WriteLine("Thread {0} begins " _
            & "and waits for the semaphore.", num)
        _pool.WaitOne()

        ' A padding interval to make the output more orderly.
        Dim padding As Integer = Interlocked.Add(_padding, 100)

        Console.WriteLine("Thread {0} enters the semaphore.", num)
        
        ' The thread's "work" consists of sleeping for 
        ' about a second. Each thread "works" a little 
        ' longer, just to make the output more orderly.
        '
        Thread.Sleep(1000 + padding)

        Console.WriteLine("Thread {0} releases the semaphore.", num)
        Console.WriteLine("Thread {0} previous semaphore count: {1}", _
            num, _
            _pool.Release())
    End Sub
End Class

備註

此建構函式會初始化未命名的號志。使用這類號志實例的所有線程都必須具有實例的參考。

如果 initialCount 小於 maximumCount ，則效果與目前線程呼叫 WaitOne (減 initialCount) maximumCount 次相同。如果您不想為建立號志的執行緒保留任何專案，請使用和 initialCount 的相同數位 maximumCount 。

另請參閱

適用於

Semaphore(Int32, Int32, String)

Source:: Semaphore.cs

Source:: Semaphore.cs

Source:: Semaphore.cs

初始化 Semaphore 類別的新執行個體，然後指定初始項目數目與並行項目的最大數目，以及選擇性地指定系統旗號物件的名稱。

public:
 Semaphore(int initialCount, int maximumCount, System::String ^ name);

public Semaphore (int initialCount, int maximumCount, string name);

public Semaphore (int initialCount, int maximumCount, string? name);

new System.Threading.Semaphore : int * int * string -> System.Threading.Semaphore

Public Sub New (initialCount As Integer, maximumCount As Integer, name As String)

參數

initialCount: Int32

可同時授與給號誌的初始要求數目。

maximumCount: Int32

可以同時授與之號誌要求的最大數目。

name: String

如果同步物件要與其他處理序共用，則為名稱；否則為 null 或空字串。名稱區分大小寫。 (\) 保留反斜線字元，而且只能用來指定命名空間。如需命名空間的詳細資訊，請參閱一節。視作業系統而定，名稱可能會有進一步的限制。例如，在 Unix 作業系統上，排除命名空間之後的名稱必須是有效的檔案名。

例外狀況

ArgumentException

initialCount 大於 maximumCount。

-或-

僅限 .NET Framework：name 的長度超過 MAX_PATH (260 個字元)。

ArgumentOutOfRangeException

maximumCount 小於 1。

-或-

initialCount 小於 0。

IOException

name 無效。這可能基於數種原因，其中包括可能由作業系統設定的一些限制，例如未知前置詞或無效字元。請注意，名稱和通用前置詞「Global\」和「Local\」會區分大小寫。

-或-

發生一些其他錯誤。 HResult 屬性可提供詳細資訊。

DirectoryNotFoundException

僅限 Windows：name 已指定未知命名空間。請參閱物件名稱 \(英文\) 以取得詳細資訊。

PathTooLongException

name 太長。長度限制可能會取決於作業系統或設定。

UnauthorizedAccessException

具名信號已存在，並且具有存取控制安全性，而使用者沒有 FullControl。

WaitHandleCannotBeOpenedException

無法建立具有所提供 name 的同步物件。不同類型的同步物件可能具有相同名稱。

範例

下列程式碼範例示範具名號志的跨進程行為。此範例會建立具名號志，其計數上限為 5，初始計數為 5。程式會對方法進行三次呼叫 WaitOne 。因此，如果您從兩個命令視窗執行編譯的範例，第二個複本會在第三次呼叫 WaitOne 時封鎖。釋放程式第一個複本中的一或多個專案，以解除封鎖第二個複本。

#using <System.dll>
using namespace System;
using namespace System::Threading;

public ref class Example
{
public:
   static void main()
   {
      // Create a Semaphore object that represents the named
      // system semaphore "SemaphoreExample3". The semaphore has a
      // maximum count of five. The initial count is also five.
      // There is no point in using a smaller initial count,
      // because the initial count is not used if this program
      // doesn't create the named system semaphore, and with
      // this method overload there is no way to tell. Thus, this
      // program assumes that it is competing with other
      // programs for the semaphore.
      //
      Semaphore^ sem = gcnew Semaphore( 5,5,L"SemaphoreExample3" );
      
      // Attempt to enter the semaphore three times. If another
      // copy of this program is already running, only the first
      // two requests can be satisfied. The third blocks. Note
      // that in a real application, timeouts should be used
      // on the WaitOne calls, to avoid deadlocks.
      //
      sem->WaitOne();
      Console::WriteLine( L"Entered the semaphore once." );
      sem->WaitOne();
      Console::WriteLine( L"Entered the semaphore twice." );
      sem->WaitOne();
      Console::WriteLine( L"Entered the semaphore three times." );
      
      // The thread executing this program has entered the
      // semaphore three times. If a second copy of the program
      // is run, it will block until this program releases the
      // semaphore at least once.
      //
      Console::WriteLine( L"Enter the number of times to call Release." );
      int n;
      if ( Int32::TryParse( Console::ReadLine(),n ) )
      {
         sem->Release( n );
      }

      int remaining = 3 - n;
      if ( remaining > 0 )
      {
         Console::WriteLine( L"Press Enter to release the remaining "
         L"count ({0}) and exit the program.", remaining );
         Console::ReadLine();
         sem->Release( remaining );
      }
   }
};

using System;
using System.Threading;

public class Example
{
    public static void Main()
    {
        // Create a Semaphore object that represents the named 
        // system semaphore "SemaphoreExample3". The semaphore has a
        // maximum count of five. The initial count is also five. 
        // There is no point in using a smaller initial count,
        // because the initial count is not used if this program
        // doesn't create the named system semaphore, and with 
        // this method overload there is no way to tell. Thus, this
        // program assumes that it is competing with other
        // programs for the semaphore.
        //
        Semaphore sem = new Semaphore(5, 5, "SemaphoreExample3");

        // Attempt to enter the semaphore three times. If another 
        // copy of this program is already running, only the first
        // two requests can be satisfied. The third blocks. Note 
        // that in a real application, timeouts should be used
        // on the WaitOne calls, to avoid deadlocks.
        //
        sem.WaitOne();
        Console.WriteLine("Entered the semaphore once.");
        sem.WaitOne();
        Console.WriteLine("Entered the semaphore twice.");
        sem.WaitOne();
        Console.WriteLine("Entered the semaphore three times.");

        // The thread executing this program has entered the 
        // semaphore three times. If a second copy of the program
        // is run, it will block until this program releases the 
        // semaphore at least once.
        //
        Console.WriteLine("Enter the number of times to call Release.");
        int n;
        if (int.TryParse(Console.ReadLine(), out n))
        {
            sem.Release(n);
        }

        int remaining = 3 - n;
        if (remaining > 0)
        {
            Console.WriteLine("Press Enter to release the remaining " +
                "count ({0}) and exit the program.", remaining);
            Console.ReadLine();
            sem.Release(remaining);
        }
    }
}

Imports System.Threading

Public Class Example

    <MTAThread> _
    Public Shared Sub Main()
        ' Create a Semaphore object that represents the named 
        ' system semaphore "SemaphoreExample3". The semaphore has a
        ' maximum count of five. The initial count is also five. 
        ' There is no point in using a smaller initial count,
        ' because the initial count is not used if this program
        ' doesn't create the named system semaphore, and with 
        ' this method overload there is no way to tell. Thus, this
        ' program assumes that it is competing with other
        ' programs for the semaphore.
        '
        Dim sem As New Semaphore(5, 5, "SemaphoreExample3")

        ' Attempt to enter the semaphore three times. If another 
        ' copy of this program is already running, only the first
        ' two requests can be satisfied. The third blocks. Note 
        ' that in a real application, timeouts should be used
        ' on the WaitOne calls, to avoid deadlocks.
        '
        sem.WaitOne()
        Console.WriteLine("Entered the semaphore once.")
        sem.WaitOne()
        Console.WriteLine("Entered the semaphore twice.")
        sem.WaitOne()
        Console.WriteLine("Entered the semaphore three times.")

        ' The thread executing this program has entered the 
        ' semaphore three times. If a second copy of the program
        ' is run, it will block until this program releases the 
        ' semaphore at least once.
        '
        Console.WriteLine("Enter the number of times to call Release.")
        Dim n As Integer
        If Integer.TryParse(Console.ReadLine(), n) Then
            sem.Release(n)
        End If

        Dim remaining As Integer = 3 - n
        If (remaining) > 0 Then
            Console.WriteLine("Press Enter to release the remaining " _
                & "count ({0}) and exit the program.", remaining)
            Console.ReadLine()
            sem.Release(remaining)
        End If

    End Sub 
End Class

備註

這個建構函式會 Semaphore 初始化物件，這個物件表示具名系統號志。您可以建立多個 Semaphore 物件，代表相同的具名系統號志。

name前面可能會加上 Global\ 或 Local\ ，以指定命名空間。 Global指定命名空間時，同步處理物件可能會與系統上的任何進程共用。 Local指定命名空間時，這也是未指定命名空間時的預設值，同步處理物件可能會與相同會話中的進程共用。在 Windows 上，會話是登入會話，而服務通常會在不同的非互動式會話中執行。在類似 Unix 的作業系統上，每個殼層都有自己的會話。會話本機同步處理物件可能適用于在進程與父子關聯性之間同步處理，而它們全都在相同的會話中執行。如需 Windows 上同步處理物件名稱的詳細資訊，請參閱物件名稱。

如果已提供， name 且要求之型別的同步處理物件已存在於命名空間中，則會使用現有的同步處理物件。如果命名空間中已經有不同類型的同步處理物件， WaitHandleCannotBeOpenedException 則會擲回。否則，會建立新的同步處理物件。

如果具名系統號志不存在，則會使用和 maximumCount 所 initialCount 指定的初始計數和最大計數來建立。如果具名系統號志已經存在， initialCount 而且 maximumCount 未使用，雖然不正確值仍然會造成例外狀況。如果您需要判斷是否已建立具名系統號志，請改用建 Semaphore(Int32, Int32, String, Boolean) 構函式多載。

重要

當您使用此建構函式多載時，建議的做法是針對和 maximumCount 指定相同的數位 initialCount 。如果 initialCount 小於 maximumCount ，而且會建立具名系統號志，則效果會與目前線程呼叫 WaitOne (maximumCount 減 initialCount 號) 次相同。不過，使用此建構函式多載，無法判斷是否已建立具名系統號志。

如果您指定 null 或的 name 空字串，就會建立本機號志，就像您已呼叫 Semaphore(Int32, Int32) 建構函式多載一樣。

因為具名號志在整個作業系統中都是可見的，所以可用來協調跨進程界限的資源使用。

如果您想要找出具名系統號志是否存在，請使用 OpenExisting 方法。方法 OpenExisting 會嘗試開啟現有的具名號志，並在系統號志不存在時擲回例外狀況。

警告

根據預設，具名號志不限於建立它的使用者。其他使用者可能能夠開啟和使用號志，包括藉由多次取得號志來干擾號志，而不會釋放旗號。若要限制特定使用者的存取，您可以使用建構函式多載，或在 SemaphoreAcl 建立具名號志時傳入 SemaphoreSecurity 。避免在執行程式碼的系統上使用具名號志，而不受存取限制。

另請參閱

適用於

Semaphore(Int32, Int32, String, Boolean)

Source:: Semaphore.cs

Source:: Semaphore.cs

Source:: Semaphore.cs

初始化 Semaphore 類別的新執行個體，然後指定初始項目物件數目與並行項目的最大數目，選擇性地指定系統號誌物件的名稱，以及指定接收值的變數，指出是否已建立新的系統號誌。

public:
 Semaphore(int initialCount, int maximumCount, System::String ^ name, [Runtime::InteropServices::Out] bool % createdNew);

public Semaphore (int initialCount, int maximumCount, string name, out bool createdNew);

public Semaphore (int initialCount, int maximumCount, string? name, out bool createdNew);

new System.Threading.Semaphore : int * int * string * bool -> System.Threading.Semaphore

Public Sub New (initialCount As Integer, maximumCount As Integer, name As String, ByRef createdNew As Boolean)

參數

initialCount: Int32

可以同時滿足之號誌要求的初始數目。

maximumCount: Int32

可以同時滿足之號誌要求的最大數目。

name: String

如果同步物件要與其他處理序共用，則為名稱；否則為 null 或空字串。名稱區分大小寫。反斜線字元 (\) 是保留的，只能用來指定命名空間。如需命名空間的詳細資訊，請參閱一節。視作業系統而定，可能會進一步限制名稱。例如，在 Unix 型作業系統上，排除命名空間之後的名稱必須是有效的檔案名。

createdNew: Boolean

這個方法傳回時，如果已建立本機號誌 (也就是說，如果 name 為 null 或空字串)，或是已建立指定的已命名系統號誌，則會包含 true；如果指定的已命名系統號誌已存在則為 false。這個參數會以未初始化的狀態傳遞。

例外狀況

ArgumentException

initialCount 大於 maximumCount。

-或-

僅限 .NET Framework：name 的長度超過 MAX_PATH (260 個字元)。

ArgumentOutOfRangeException

maximumCount 小於 1。

-或-

initialCount 小於 0。

IOException

-或-

發生一些其他錯誤。 HResult 屬性可提供詳細資訊。

DirectoryNotFoundException

僅限 Windows：name 已指定未知命名空間。請參閱物件名稱 \(英文\) 以取得詳細資訊。

PathTooLongException

name 太長。長度限制可能會取決於作業系統或設定。

UnauthorizedAccessException

具名信號已存在，並且具有存取控制安全性，而使用者沒有 FullControl。

WaitHandleCannotBeOpenedException

無法建立具有所提供 name 的同步物件。不同類型的同步物件可能具有相同名稱。

範例

下列程式碼範例示範具名號志的跨進程行為。此範例會建立具名號志，其計數上限為 5，初始計數為 2。也就是說，它會為呼叫建構函式的執行緒保留三個專案。如果 createNew 為 false ，則程式會對方法進行三次呼叫 WaitOne 。因此，如果您從兩個命令視窗執行編譯的範例，第二個複本會在第三次呼叫 WaitOne 時封鎖。釋放程式第一個複本中的一或多個專案，以解除封鎖第二個複本。

#using <System.dll>
using namespace System;
using namespace System::Threading;

public ref class Example
{
public:
   static void main()
   {
      // The value of this variable is set by the semaphore
      // constructor. It is true if the named system semaphore was
      // created, and false if the named semaphore already existed.
      //
      bool semaphoreWasCreated;
      
      // Create a Semaphore object that represents the named
      // system semaphore "SemaphoreExample". The semaphore has a
      // maximum count of five, and an initial count of two. The
      // Boolean value that indicates creation of the underlying
      // system object is placed in semaphoreWasCreated.
      //
      Semaphore^ sem = gcnew Semaphore( 2,5,L"SemaphoreExample",
         semaphoreWasCreated );
      if ( semaphoreWasCreated )
      {
         // If the named system semaphore was created, its count is
         // set to the initial count requested in the constructor.
         // In effect, the current thread has entered the semaphore
         // three times.
         //
         Console::WriteLine( L"Entered the semaphore three times." );
      }
      else
      {
         // If the named system semaphore was not created,
         // attempt to enter it three times. If another copy of
         // this program is already running, only the first two
         // requests can be satisfied. The third blocks.
         //
         sem->WaitOne();
         Console::WriteLine( L"Entered the semaphore once." );
         sem->WaitOne();
         Console::WriteLine( L"Entered the semaphore twice." );
         sem->WaitOne();
         Console::WriteLine( L"Entered the semaphore three times." );
      }
      
      // The thread executing this program has entered the
      // semaphore three times. If a second copy of the program
      // is run, it will block until this program releases the
      // semaphore at least once.
      //
      Console::WriteLine( L"Enter the number of times to call Release." );
      int n;
      if ( Int32::TryParse( Console::ReadLine(), n ) )
      {
         sem->Release( n );
      }

      int remaining = 3 - n;
      if ( remaining > 0 )
      {
         Console::WriteLine( L"Press Enter to release the remaining "
         L"count ({0}) and exit the program.", remaining );
         Console::ReadLine();
         sem->Release( remaining );
      }
   }
};

using System;
using System.Threading;

public class Example
{
    public static void Main()
    {
        // The value of this variable is set by the semaphore
        // constructor. It is true if the named system semaphore was
        // created, and false if the named semaphore already existed.
        //
        bool semaphoreWasCreated;

        // Create a Semaphore object that represents the named 
        // system semaphore "SemaphoreExample". The semaphore has a
        // maximum count of five, and an initial count of two. The
        // Boolean value that indicates creation of the underlying 
        // system object is placed in semaphoreWasCreated.
        //
        Semaphore sem = new Semaphore(2, 5, "SemaphoreExample", 
            out semaphoreWasCreated);

        if (semaphoreWasCreated)
        {
            // If the named system semaphore was created, its count is
            // set to the initial count requested in the constructor.
            // In effect, the current thread has entered the semaphore
            // three times.
            // 
            Console.WriteLine("Entered the semaphore three times.");
        }
        else
        {      
            // If the named system semaphore was not created,  
            // attempt to enter it three times. If another copy of
            // this program is already running, only the first two
            // requests can be satisfied. The third blocks.
            //
            sem.WaitOne();
            Console.WriteLine("Entered the semaphore once.");
            sem.WaitOne();
            Console.WriteLine("Entered the semaphore twice.");
            sem.WaitOne();
            Console.WriteLine("Entered the semaphore three times.");
        }

        // The thread executing this program has entered the 
        // semaphore three times. If a second copy of the program
        // is run, it will block until this program releases the 
        // semaphore at least once.
        //
        Console.WriteLine("Enter the number of times to call Release.");
        int n;
        if (int.TryParse(Console.ReadLine(), out n))
        {
            sem.Release(n);
        }

        int remaining = 3 - n;
        if (remaining > 0)
        {
            Console.WriteLine("Press Enter to release the remaining " +
                "count ({0}) and exit the program.", remaining);
            Console.ReadLine();
            sem.Release(remaining);
        }
    } 
}

Imports System.Threading

Public Class Example

    <MTAThread> _
    Public Shared Sub Main()
        ' The value of this variable is set by the semaphore
        ' constructor. It is True if the named system semaphore was
        ' created, and False if the named semaphore already existed.
        '
        Dim semaphoreWasCreated As Boolean

        ' Create a Semaphore object that represents the named 
        ' system semaphore "SemaphoreExample". The semaphore has a
        ' maximum count of five, and an initial count of two. The
        ' Boolean value that indicates creation of the underlying 
        ' system object is placed in semaphoreWasCreated.
        '
        Dim sem As New Semaphore(2, 5, "SemaphoreExample", _
            semaphoreWasCreated)

        If semaphoreWasCreated Then
            ' If the named system semaphore was created, its count is
            ' set to the initial count requested in the constructor.
            ' In effect, the current thread has entered the semaphore
            ' three times.
            ' 
            Console.WriteLine("Entered the semaphore three times.")
        Else
            ' If the named system semaphore was not created,  
            ' attempt to enter it three times. If another copy of
            ' this program is already running, only the first two
            ' requests can be satisfied. The third blocks.
            '
            sem.WaitOne()
            Console.WriteLine("Entered the semaphore once.")
            sem.WaitOne()
            Console.WriteLine("Entered the semaphore twice.")
            sem.WaitOne()
            Console.WriteLine("Entered the semaphore three times.")
        End If

        ' The thread executing this program has entered the 
        ' semaphore three times. If a second copy of the program
        ' is run, it will block until this program releases the 
        ' semaphore at least once.
        '
        Console.WriteLine("Enter the number of times to call Release.")
        Dim n As Integer
        If Integer.TryParse(Console.ReadLine(), n) Then
            sem.Release(n)
        End If

        Dim remaining As Integer = 3 - n
        If (remaining) > 0 Then
            Console.WriteLine("Press Enter to release the remaining " _
                & "count ({0}) and exit the program.", remaining)
            Console.ReadLine()
            sem.Release(remaining)
        End If

    End Sub 
End Class

備註

name前面可能會加上 Global\ 或 Local\ ，以指定命名空間。 Global指定命名空間時，同步處理物件可能會與系統上的任何進程共用。 Local指定命名空間時，這也是未指定命名空間時的預設值，同步處理物件可能會與相同會話中的進程共用。在 Windows 上，會話是登入會話，服務通常會在不同的非互動式會話中執行。在類似 Unix 的作業系統上，每個殼層都有自己的會話。會話本機同步處理物件可能適用于在進程與父/子關聯性之間同步處理，其中它們全都在相同會話中執行。如需 Windows 上同步處理物件名稱的詳細資訊，請參閱物件名稱。

name如果已提供，且要求的型別同步處理物件已存在於命名空間中，則會使用現有的同步處理物件。如果命名空間中已經存在不同類型的同步處理物件， WaitHandleCannotBeOpenedException 則會擲回。否則，會建立新的同步處理物件。

這個建構函式會 Semaphore 初始化物件，此物件表示具名系統旗號。您可以建立多個 Semaphore 物件，代表相同的具名系統旗號。

如果具名系統旗號不存在，則會使用和所 initialCountmaximumCount 指定的初始計數和最大計數來建立。如果具名系統旗號已經存在，而且 maximumCount 未使用， initialCount 但不正確值仍會造成例外狀況。用來 createdNew 判斷是否已建立系統旗號。

如果 initialCount 小於 maximumCount ，且 createdNew 為 true ，則效果會與目前線程呼叫 WaitOne (maximumCount 減) initialCount 次相同。

如果您為指定 null 或空字串 name ，就會建立本機旗號，就像您呼叫 Semaphore(Int32, Int32) 建構函式多載一樣。在此情況下， createdNew 一律 true 為。

由於在作業系統中可以看到具名旗號，因此可用來協調跨進程界限的資源使用。

警告

根據預設，具名旗號不限於建立它的使用者。其他使用者可能能夠開啟和使用旗號，包括藉由取得信號多次而干擾旗號，而不會釋放旗號。若要限制特定使用者的存取權，您可以使用建構函式多載，或在 SemaphoreAcl 建立具名旗號時傳入 SemaphoreSecurity 。避免在執行程式碼的系統上使用具名旗號，而不需存取限制。

另請參閱

適用於

Semaphore(Int32, Int32, String, Boolean, SemaphoreSecurity)

初始化 Semaphore 類別的新執行個體，然後指定初始項目數目與並行項目的最大數目，選擇性地指定系統號誌物件的名稱，指定接收值的變數 (以指示是否已建立新的系統號誌)，以及指定系統號誌的安全性存取控制。

public:
 Semaphore(int initialCount, int maximumCount, System::String ^ name, [Runtime::InteropServices::Out] bool % createdNew, System::Security::AccessControl::SemaphoreSecurity ^ semaphoreSecurity);

public Semaphore (int initialCount, int maximumCount, string name, out bool createdNew, System.Security.AccessControl.SemaphoreSecurity semaphoreSecurity);

new System.Threading.Semaphore : int * int * string * bool * System.Security.AccessControl.SemaphoreSecurity -> System.Threading.Semaphore

Public Sub New (initialCount As Integer, maximumCount As Integer, name As String, ByRef createdNew As Boolean, semaphoreSecurity As SemaphoreSecurity)

參數

initialCount: Int32

可以同時滿足之號誌要求的初始數目。

maximumCount: Int32

可以同時滿足之號誌要求的最大數目。

name: String

createdNew: Boolean

semaphoreSecurity: SemaphoreSecurity

SemaphoreSecurity 物件，表示要套用到具名系統旗號的存取控制安全性。

例外狀況

ArgumentException

initialCount 大於 maximumCount。

-或-

僅限 .NET Framework：name 的長度超過 MAX_PATH (260 個字元)。

ArgumentOutOfRangeException

maximumCount 小於 1。

-或-

initialCount 小於 0。

UnauthorizedAccessException

具名信號已存在，並且具有存取控制安全性，而使用者沒有 FullControl。

IOException

-或-

發生一些其他錯誤。 HResult 屬性可提供詳細資訊。

DirectoryNotFoundException

僅限 Windows：name 已指定未知命名空間。請參閱物件名稱 \(英文\) 以取得詳細資訊。

PathTooLongException

name 太長。長度限制可能會取決於作業系統或設定。

WaitHandleCannotBeOpenedException

無法建立具有所提供 name 的同步物件。不同類型的同步物件可能具有相同名稱。

範例

下列程式碼範例示範具有存取控制安全性之具名旗號的跨進程行為。此範例會 OpenExisting(String) 使用方法多載來測試具名旗號是否存在。如果旗號不存在，則會以最多兩個計數建立，且存取控制安全性會拒絕目前使用者使用旗號的許可權，但授與讀取和變更旗號的許可權。如果您從兩個命令視窗執行編譯的範例，第二個複本會在呼叫 OpenExisting(String) 方法時擲回存取違規例外狀況。攔截到例外狀況，而此範例會 OpenExisting(String, SemaphoreRights) 使用方法多載來開啟旗號，並具有讀取和變更許可權所需的許可權。

變更許可權之後，會以輸入和釋放所需的許可權開啟旗號。如果您從第三個命令視窗執行編譯的範例，它會使用新的許可權來執行。

#using <System.dll>
using namespace System;
using namespace System::Threading;
using namespace System::Security::AccessControl;
using namespace System::Security::Permissions;

public ref class Example
{
public:
   [SecurityPermissionAttribute(SecurityAction::Demand, Flags = SecurityPermissionFlag::UnmanagedCode)]
   static void main()
   {
      String^ semaphoreName = L"SemaphoreExample5";

      Semaphore^ sem = nullptr;
      bool doesNotExist = false;
      bool unauthorized = false;
      
      // Attempt to open the named semaphore.
      try
      {
         // Open the semaphore with (SemaphoreRights.Synchronize
         // | SemaphoreRights.Modify), to enter and release the
         // named semaphore.
         //
         sem = Semaphore::OpenExisting( semaphoreName );
      }
      catch ( WaitHandleCannotBeOpenedException^ ex ) 
      {
         Console::WriteLine( L"Semaphore does not exist." );
         doesNotExist = true;
      }
      catch ( UnauthorizedAccessException^ ex ) 
      {
         Console::WriteLine( L"Unauthorized access: {0}", ex->Message );
         unauthorized = true;
      }

      // There are three cases: (1) The semaphore does not exist.
      // (2) The semaphore exists, but the current user doesn't
      // have access. (3) The semaphore exists and the user has
      // access.
      //
      if ( doesNotExist )
      {
         // The semaphore does not exist, so create it.
         //
         // The value of this variable is set by the semaphore
         // constructor. It is true if the named system semaphore was
         // created, and false if the named semaphore already existed.
         //
         bool semaphoreWasCreated;
         
         // Create an access control list (ACL) that denies the
         // current user the right to enter or release the
         // semaphore, but allows the right to read and change
         // security information for the semaphore.
         //
         String^ user = String::Concat( Environment::UserDomainName,
            L"\\", Environment::UserName );
         SemaphoreSecurity^ semSec = gcnew SemaphoreSecurity;

         SemaphoreAccessRule^ rule = gcnew SemaphoreAccessRule( user,
            static_cast<SemaphoreRights>(
               SemaphoreRights::Synchronize |
               SemaphoreRights::Modify ),
            AccessControlType::Deny );
         semSec->AddAccessRule( rule );

         rule = gcnew SemaphoreAccessRule( user,
            static_cast<SemaphoreRights>(
               SemaphoreRights::ReadPermissions |
               SemaphoreRights::ChangePermissions ),
            AccessControlType::Allow );
         semSec->AddAccessRule( rule );
         
         // Create a Semaphore object that represents the system
         // semaphore named by the constant 'semaphoreName', with
         // maximum count three, initial count three, and the
         // specified security access. The Boolean value that
         // indicates creation of the underlying system object is
         // placed in semaphoreWasCreated.
         //
         sem = gcnew Semaphore( 3,3,semaphoreName,semaphoreWasCreated,semSec );
         
         // If the named system semaphore was created, it can be
         // used by the current instance of this program, even
         // though the current user is denied access. The current
         // program enters the semaphore. Otherwise, exit the
         // program.
         //
         if ( semaphoreWasCreated )
         {
            Console::WriteLine( L"Created the semaphore." );
         }
         else
         {
            Console::WriteLine( L"Unable to create the semaphore." );
            return;
         }

      }
      else if ( unauthorized )
      {
         // Open the semaphore to read and change the access
         // control security. The access control security defined
         // above allows the current user to do this.
         //
         try
         {
            sem = Semaphore::OpenExisting( semaphoreName,
               static_cast<SemaphoreRights>(
                  SemaphoreRights::ReadPermissions |
                  SemaphoreRights::ChangePermissions ));
            
            // Get the current ACL. This requires
            // SemaphoreRights.ReadPermissions.
            SemaphoreSecurity^ semSec = sem->GetAccessControl();

            String^ user = String::Concat( Environment::UserDomainName,
               L"\\", Environment::UserName );
            
            // First, the rule that denied the current user
            // the right to enter and release the semaphore must
            // be removed.
            SemaphoreAccessRule^ rule = gcnew SemaphoreAccessRule( user,
               static_cast<SemaphoreRights>(
                  SemaphoreRights::Synchronize |
                  SemaphoreRights::Modify ),
               AccessControlType::Deny );
            semSec->RemoveAccessRule( rule );
            
            // Now grant the user the correct rights.
            //
            rule = gcnew SemaphoreAccessRule( user,
               static_cast<SemaphoreRights>(
                  SemaphoreRights::Synchronize |
                  SemaphoreRights::Modify ),
               AccessControlType::Allow );
            semSec->AddAccessRule( rule );
            
            // Update the ACL. This requires
            // SemaphoreRights.ChangePermissions.
            sem->SetAccessControl( semSec );

            Console::WriteLine( L"Updated semaphore security." );
            
            // Open the semaphore with (SemaphoreRights.Synchronize
            // | SemaphoreRights.Modify), the rights required to
            // enter and release the semaphore.
            //
            sem = Semaphore::OpenExisting( semaphoreName );

         }
         catch ( UnauthorizedAccessException^ ex ) 
         {
            Console::WriteLine( L"Unable to change permissions: {0}", ex->Message );
            return;
         }
      }
      
      // Enter the semaphore, and hold it until the program
      // exits.
      //
      try
      {
         sem->WaitOne();
         Console::WriteLine( L"Entered the semaphore." );
         Console::WriteLine( L"Press the Enter key to exit." );
         Console::ReadLine();
         sem->Release();
      }
      catch ( UnauthorizedAccessException^ ex ) 
      {
         Console::WriteLine( L"Unauthorized access: {0}", ex->Message );
      }
   }
};

using System;
using System.Threading;
using System.Security.AccessControl;

internal class Example
{
    internal static void Main()
    {
        const string semaphoreName = "SemaphoreExample5";

        Semaphore sem = null;
        bool doesNotExist = false;
        bool unauthorized = false;

        // Attempt to open the named semaphore.
        try
        {
            // Open the semaphore with (SemaphoreRights.Synchronize
            // | SemaphoreRights.Modify), to enter and release the
            // named semaphore.
            //
            sem = Semaphore.OpenExisting(semaphoreName);
        }
        catch(WaitHandleCannotBeOpenedException)
        {
            Console.WriteLine("Semaphore does not exist.");
            doesNotExist = true;
        }
        catch(UnauthorizedAccessException ex)
        {
            Console.WriteLine("Unauthorized access: {0}", ex.Message);
            unauthorized = true;
        }

        // There are three cases: (1) The semaphore does not exist.
        // (2) The semaphore exists, but the current user doesn't 
        // have access. (3) The semaphore exists and the user has
        // access.
        //
        if (doesNotExist)
        {
            // The semaphore does not exist, so create it.
            //
            // The value of this variable is set by the semaphore
            // constructor. It is true if the named system semaphore was
            // created, and false if the named semaphore already existed.
            //
            bool semaphoreWasCreated;

            // Create an access control list (ACL) that denies the
            // current user the right to enter or release the 
            // semaphore, but allows the right to read and change
            // security information for the semaphore.
            //
            string user = Environment.UserDomainName + "\\" 
                + Environment.UserName;
            SemaphoreSecurity semSec = new SemaphoreSecurity();

            SemaphoreAccessRule rule = new SemaphoreAccessRule(
                user, 
                SemaphoreRights.Synchronize | SemaphoreRights.Modify, 
                AccessControlType.Deny);
            semSec.AddAccessRule(rule);

            rule = new SemaphoreAccessRule(
                user, 
                SemaphoreRights.ReadPermissions | SemaphoreRights.ChangePermissions,
                AccessControlType.Allow);
            semSec.AddAccessRule(rule);

            // Create a Semaphore object that represents the system
            // semaphore named by the constant 'semaphoreName', with
            // maximum count three, initial count three, and the
            // specified security access. The Boolean value that 
            // indicates creation of the underlying system object is
            // placed in semaphoreWasCreated.
            //
            sem = new Semaphore(3, 3, semaphoreName, 
                out semaphoreWasCreated, semSec);

            // If the named system semaphore was created, it can be
            // used by the current instance of this program, even 
            // though the current user is denied access. The current
            // program enters the semaphore. Otherwise, exit the
            // program.
            // 
            if (semaphoreWasCreated)
            {
                Console.WriteLine("Created the semaphore.");
            }
            else
            {
                Console.WriteLine("Unable to create the semaphore.");
                return;
            }
        }
        else if (unauthorized)
        {
            // Open the semaphore to read and change the access
            // control security. The access control security defined
            // above allows the current user to do this.
            //
            try
            {
                sem = Semaphore.OpenExisting(
                    semaphoreName, 
                    SemaphoreRights.ReadPermissions 
                        | SemaphoreRights.ChangePermissions);

                // Get the current ACL. This requires 
                // SemaphoreRights.ReadPermissions.
                SemaphoreSecurity semSec = sem.GetAccessControl();
                
                string user = Environment.UserDomainName + "\\" 
                    + Environment.UserName;

                // First, the rule that denied the current user 
                // the right to enter and release the semaphore must
                // be removed.
                SemaphoreAccessRule rule = new SemaphoreAccessRule(
                    user, 
                    SemaphoreRights.Synchronize | SemaphoreRights.Modify, 
                    AccessControlType.Deny);
                semSec.RemoveAccessRule(rule);

                // Now grant the user the correct rights.
                // 
                rule = new SemaphoreAccessRule(user, 
                     SemaphoreRights.Synchronize | SemaphoreRights.Modify, 
                     AccessControlType.Allow);
                semSec.AddAccessRule(rule);

                // Update the ACL. This requires
                // SemaphoreRights.ChangePermissions.
                sem.SetAccessControl(semSec);

                Console.WriteLine("Updated semaphore security.");

                // Open the semaphore with (SemaphoreRights.Synchronize 
                // | SemaphoreRights.Modify), the rights required to
                // enter and release the semaphore.
                //
                sem = Semaphore.OpenExisting(semaphoreName);
            }
            catch(UnauthorizedAccessException ex)
            {
                Console.WriteLine("Unable to change permissions: {0}", ex.Message);
                return;
            }
        }

        // Enter the semaphore, and hold it until the program
        // exits.
        //
        try
        {
            sem.WaitOne();
            Console.WriteLine("Entered the semaphore.");
            Console.WriteLine("Press the Enter key to exit.");
            Console.ReadLine();
            sem.Release();
        }
        catch(UnauthorizedAccessException ex)
        {
            Console.WriteLine("Unauthorized access: {0}", ex.Message);
        }
    }
}

Imports System.Threading
Imports System.Security.AccessControl

Friend Class Example

    <MTAThread> _
    Friend Shared Sub Main()
        Const semaphoreName As String = "SemaphoreExample5"

        Dim sem As Semaphore = Nothing
        Dim doesNotExist as Boolean = False
        Dim unauthorized As Boolean = False

        ' Attempt to open the named semaphore.
        Try
            ' Open the semaphore with (SemaphoreRights.Synchronize
            ' Or SemaphoreRights.Modify), to enter and release the
            ' named semaphore.
            '
            sem = Semaphore.OpenExisting(semaphoreName)
        Catch ex As WaitHandleCannotBeOpenedException
            Console.WriteLine("Semaphore does not exist.")
            doesNotExist = True
        Catch ex As UnauthorizedAccessException
            Console.WriteLine("Unauthorized access: {0}", ex.Message)
            unauthorized = True
        End Try

        ' There are three cases: (1) The semaphore does not exist.
        ' (2) The semaphore exists, but the current user doesn't 
        ' have access. (3) The semaphore exists and the user has
        ' access.
        '
        If doesNotExist Then
            ' The semaphore does not exist, so create it.
            '
            ' The value of this variable is set by the semaphore
            ' constructor. It is True if the named system semaphore was
            ' created, and False if the named semaphore already existed.
            '
            Dim semaphoreWasCreated As Boolean

            ' Create an access control list (ACL) that denies the
            ' current user the right to enter or release the 
            ' semaphore, but allows the right to read and change
            ' security information for the semaphore.
            '
            Dim user As String = Environment.UserDomainName _ 
                & "\" & Environment.UserName
            Dim semSec As New SemaphoreSecurity()

            Dim rule As New SemaphoreAccessRule(user, _
                SemaphoreRights.Synchronize Or SemaphoreRights.Modify, _
                AccessControlType.Deny)
            semSec.AddAccessRule(rule)

            rule = New SemaphoreAccessRule(user, _
                SemaphoreRights.ReadPermissions Or _
                SemaphoreRights.ChangePermissions, _
                AccessControlType.Allow)
            semSec.AddAccessRule(rule)

            ' Create a Semaphore object that represents the system
            ' semaphore named by the constant 'semaphoreName', with
            ' maximum count three, initial count three, and the
            ' specified security access. The Boolean value that 
            ' indicates creation of the underlying system object is
            ' placed in semaphoreWasCreated.
            '
            sem = New Semaphore(3, 3, semaphoreName, _
                semaphoreWasCreated, semSec)

            ' If the named system semaphore was created, it can be
            ' used by the current instance of this program, even 
            ' though the current user is denied access. The current
            ' program enters the semaphore. Otherwise, exit the
            ' program.
            ' 
            If semaphoreWasCreated Then
                Console.WriteLine("Created the semaphore.")
            Else
                Console.WriteLine("Unable to create the semaphore.")
                Return
            End If

        ElseIf unauthorized Then

            ' Open the semaphore to read and change the access
            ' control security. The access control security defined
            ' above allows the current user to do this.
            '
            Try
                sem = Semaphore.OpenExisting(semaphoreName, _
                    SemaphoreRights.ReadPermissions Or _
                    SemaphoreRights.ChangePermissions)

                ' Get the current ACL. This requires 
                ' SemaphoreRights.ReadPermissions.
                Dim semSec As SemaphoreSecurity = sem.GetAccessControl()
                
                Dim user As String = Environment.UserDomainName _ 
                    & "\" & Environment.UserName

                ' First, the rule that denied the current user 
                ' the right to enter and release the semaphore must
                ' be removed.
                Dim rule As New SemaphoreAccessRule(user, _
                    SemaphoreRights.Synchronize Or SemaphoreRights.Modify, _
                    AccessControlType.Deny)
                semSec.RemoveAccessRule(rule)

                ' Now grant the user the correct rights.
                ' 
                rule = New SemaphoreAccessRule(user, _
                    SemaphoreRights.Synchronize Or SemaphoreRights.Modify, _
                    AccessControlType.Allow)
                semSec.AddAccessRule(rule)

                ' Update the ACL. This requires
                ' SemaphoreRights.ChangePermissions.
                sem.SetAccessControl(semSec)

                Console.WriteLine("Updated semaphore security.")

                ' Open the semaphore with (SemaphoreRights.Synchronize 
                ' Or SemaphoreRights.Modify), the rights required to
                ' enter and release the semaphore.
                '
                sem = Semaphore.OpenExisting(semaphoreName)

            Catch ex As UnauthorizedAccessException
                Console.WriteLine("Unable to change permissions: {0}", _
                    ex.Message)
                Return
            End Try

        End If

        ' Enter the semaphore, and hold it until the program
        ' exits.
        '
        Try
            sem.WaitOne()
            Console.WriteLine("Entered the semaphore.")
            Console.WriteLine("Press the Enter key to exit.")
            Console.ReadLine()
            sem.Release()
        Catch ex As UnauthorizedAccessException
            Console.WriteLine("Unauthorized access: {0}", _
                ex.Message)
        End Try
    End Sub 
End Class

備註

使用此建構函式在建立時將存取控制安全性套用至具名系統旗號，以防止其他程式碼控制旗號。

這個建構函式會 Semaphore 初始化物件，此物件表示具名系統旗號。您可以建立多個 Semaphore 物件，代表相同的具名系統旗號。

如果具名系統旗號不存在，則會使用指定的存取控制安全性來建立它。如果具名旗號存在，則會忽略指定的存取控制安全性。

注意

即使 semaphoreSecurity 拒絕或無法將某些存取權限授與目前使用者，呼叫端仍可完全控制新建立 Semaphore 的物件。不過，如果目前使用者嘗試取得另一個 Semaphore 物件來代表相同的具名旗號，請使用建構函式或 OpenExisting 方法，套用 Windows 存取控制安全性。

如果具名系統旗號不存在，則會使用和所 initialCountmaximumCount 指定的初始計數和最大計數來建立。如果具名系統旗號已經存在，而且 maximumCount 未使用， initialCount 但不正確值仍會造成例外狀況。 createdNew使用參數來判斷系統旗號是否由這個建構函式建立。

如果 initialCount 小於 maximumCount ，且 createdNew 為 true ，則效果會與目前線程呼叫 WaitOne (maximumCount 減) initialCount 次相同。

如果您為指定 null 或空字串 name ，就會建立本機旗號，就像您呼叫 Semaphore(Int32, Int32) 建構函式多載一樣。在此情況下， createdNew 一律 true 為。

由於在作業系統中可以看到具名旗號，因此可用來協調跨進程界限的資源使用。

警告

根據預設，具名旗號不限於建立它的使用者。其他使用者可能能夠開啟和使用旗號，包括藉由取得信號多次而干擾旗號，而不會釋放旗號。若要限制特定使用者的存取權，您可以在建立具名旗號時傳入 SemaphoreSecurity 。避免在執行程式碼的系統上使用具名旗號，而不需存取限制。

另請參閱

適用於

Semaphore 建構函式

定義

多載

Semaphore(Int32, Int32)

參數

例外狀況

範例

備註

另請參閱

適用於

Semaphore(Int32, Int32, String)

參數

例外狀況

範例

備註

另請參閱

適用於

Semaphore(Int32, Int32, String, Boolean)

參數

例外狀況

範例

備註

另請參閱

適用於

Semaphore(Int32, Int32, String, Boolean, SemaphoreSecurity)

參數

例外狀況

範例

備註

另請參閱

適用於

意見反應

其他資源