スレッドの作成
オペレーティング システム プロセスが作成されると、オペレーティング システムは、元のアプリケーション ドメインを含め、そのプロセスにコードを実行するためのスレッドを挿入します。その時点からは、アプリケーション ドメインを作成したり、破棄したりする場合に、必ずしもオペレーティング システム スレッドを作成したり、破棄したりする必要はありません。実行されているコードがマネージ コードの場合は、スレッド クラス Thread.CurrentThread で静的プロパティを取得すると、現在のアプリケーション ドメインで実行しているスレッドの Thread オブジェクトを取得できます。
Thread オブジェクトの新しいインスタンスを作成すると、新しいマネージ スレッドが作成されます。Thread のコンストラクタは、Thread.Start の呼び出し時に新しい Thread によって呼び出されるメソッドをラップする ThreadStart デリゲートを、自身の唯一のパラメータとして受け取ります。Thread.Start を複数回呼び出すと、ThreadStateException がスローされます。
Thread.Start は非同期要求をシステムに送信し、その呼び出しは、おそらく新しいスレッドが実際に起動される前に戻ります。Thread.ThreadState と Thread.IsAlive を使用すると、いつでもスレッドの状態を確認できます。Thread.Abort は、スレッドをガベージ コレクション用にマークして、アボートします。別のオブジェクトでインスタンス メソッドと静的メソッドを呼び出すために 2 つの新しいスレッドを作成するコード例を次に示します。
Imports System
Imports System.Threading
Public Class ServerClass
' The method that will be called when the thread is started.
Public Sub InstanceMethod()
Console.WriteLine("ServerClass.InstanceMethod is running on another thread.")
Thread.Sleep(3000) ' Pause for a moment to provide a delay to make threads more apparent.
Console.WriteLine("The instance method called by the worker thread has ended.")
End Sub 'InstanceMethod
Public Shared Sub StaticMethod()
Console.WriteLine("ServerClass.StaticMethod is running on another thread.")
Thread.Sleep(5000) ' Pause for a moment to provide a delay to make threads more apparent.
Console.WriteLine("The static method called by the worker thread has ended.")
End Sub 'StaticMethod
End Class 'ServerClass
Public Class Simple
Public Shared Sub Main()
Console.WriteLine("Thread Simple Sample")
Dim serverObject As New ServerClass()
' Create the thread object, passing in the
' serverObject.InstanceMethod method using a
' ThreadStart delegate.
Dim InstanceCaller As New Thread(New ThreadStart(AddressOf serverObject.InstanceMethod))
' Start the thread.
InstanceCaller.Start()
Console.WriteLine("The Main() thread calls this after starting the new InstanceCaller thread.")
' Create the thread object, passing in the serverObject.StaticMethod
' method using a ThreadStart delegate.
Dim StaticCaller As New Thread(New ThreadStart(AddressOf ServerClass.StaticMethod))
' Start the thread.
StaticCaller.Start()
Console.WriteLine("The Main() thread calls this after starting the new StaticCaller threads.")
End Sub 'Main
End Class 'Simple
[C#]
using System;
using System.Threading;
public class ServerClass{
// The method that will be called when the thread is started.
public void InstanceMethod(){
Console.WriteLine("ServerClass.InstanceMethod is running on another thread.");
// Pause for a moment to provide a delay to make threads more apparent.
Thread.Sleep(3000);
Console.WriteLine("The instance method called by the worker thread has ended.");
}
public static void StaticMethod(){
Console.WriteLine("ServerClass.StaticMethod is running on another thread.");
// Pause for a moment to provide a delay to make threads more apparent.
Thread.Sleep(5000);
Console.WriteLine("The static method called by the worker thread has ended.");
}
}
public class Simple{
public static int Main(String[] args){
Console.WriteLine("Thread Simple Sample");
ServerClass serverObject = new ServerClass();
// Create the thread object, passing in the
// serverObject.InstanceMethod method using a ThreadStart delegate.
Thread InstanceCaller = new Thread(new ThreadStart(serverObject.InstanceMethod));
// Start the thread.
InstanceCaller.Start();
Console.WriteLine("The Main() thread calls this after starting the new InstanceCaller thread.");
// Create the thread object, passing in the
// serverObject.StaticMethod method using a ThreadStart delegate.
Thread StaticCaller = new Thread(new ThreadStart(ServerClass.StaticMethod));
// Start the thread.
StaticCaller.Start();
Console.WriteLine("The Main() thread calls this after starting the new StaticCaller threads.");
return 0;
}
}
スレッドへのデータの渡し方
ThreadStart デリゲートは、パラメータを受け取らず、戻り値もありません。つまり、スレッドを開始するメソッドで、パラメータを受け取ったり、値を返したりすることはできません。
- スレッドにデータを渡すには、データとスレッド メソッドを保持するオブジェクトを作成します。2 つのコード例を以下に示します。
- スレッド メソッドの結果を取得するには、コールバック メソッドを使用できます。以下の 2 番目のコードで、その例を示します。
Imports System
Imports System.Threading
' The ThreadWithState class contains the information needed for
' a task, and the method that executes the task.
'
Public Class ThreadWithState
' State information used in the task.
Private boilerplate As String
Private value As Integer
' The constructor obtains the state information.
Public Sub New(ByVal text As String, ByVal number As Integer)
boilerplate = text
value = number
End Sub
' The thread procedure performs the task, such as formatting
' and printing a document.
Public Sub ThreadProc()
Console.WriteLine(boilerplate, value)
End Sub
End Class
' Entry point for the example.
'
Public Class Example
Public Shared Sub Main()
' Supply the state information required by the task.
Dim tws As New ThreadWithState("This report displays the number {0}.", 42)
' Create a thread to execute the task, and then
' start the thread.
Dim t As New Thread(AddressOf tws.ThreadProc)
t.Start()
Console.WriteLine("Main thread does some work, then waits.")
t.Join()
Console.WriteLine("Independent task has completed; main thread ends.")
End Sub
End Class
[C#]
using System;
using System.Threading;
// The ThreadWithState class contains the information needed for
// a task, and the method that executes the task.
//
public class ThreadWithState {
// State information used in the task.
private string boilerplate;
private int value;
// The constructor obtains the state information.
public ThreadWithState(string text, int number) {
boilerplate = text;
value = number;
}
// The thread procedure performs the task, such as formatting
// and printing a document.
public void ThreadProc() {
Console.WriteLine(boilerplate, value);
}
}
// Entry point for the example.
//
public class Example {
public static void Main() {
// Supply the state information required by the task.
ThreadWithState tws =
new ThreadWithState("This report displays the number {0}.", 42);
// Create a thread to execute the task, and then
// start the thread.
Thread t = new Thread(new ThreadStart(tws.ThreadProc));
t.Start();
Console.WriteLine("Main thread does some work, then waits.");
t.Join();
Console.WriteLine("Independent task has completed; main thread ends.");
}
}
コールバック メソッドによるデータの取得
スレッドからデータを取得するコールバック メソッドの例を次に示します。データとスレッド メソッドを含むクラスのコンストラクタは、コールバック メソッドを表すデリゲートも受け取ります。スレッド メソッドの最後で、コールバック デリゲートを呼び出します。
Imports System
Imports System.Threading
' The ThreadWithState class contains the information needed for
' a task, the method that executes the task, and a delegate
' to call when the task is complete.
'
Public Class ThreadWithState
' State information used in the task.
Private boilerplate As String
Private value As Integer
' Delegate used to execute the callback method when the
' task is complete.
Private callback As ExampleCallback
' The constructor obtains the state information and the
' callback delegate.
Public Sub New(ByVal text As String, ByVal number As Integer, _
ByVal callbackDelegate As ExampleCallback)
boilerplate = text
value = number
callback = callbackDelegate
End Sub
' The thread procedure performs the task, such as
' formatting and printing a document, and then invokes
' the callback delegate with the number of lines printed.
Public Sub ThreadProc()
Console.WriteLine(boilerplate, value)
If Not callback Is Nothing Then callback(1)
End Sub
End Class
' Delegate that defines the signature for the callback method.
'
Public Delegate Sub ExampleCallback(ByVal lineCount As Integer)
' Entry point for the example.
'
Public Class Example
Public Shared Sub Main()
' Supply the state information required by the task.
Dim tws As New ThreadWithState( _
"This report displays the number {0}.", _
42, _
New ExampleCallback(AddressOf ResultCallback) _
)
Dim t As New Thread(AddressOf tws.ThreadProc)
t.Start()
Console.WriteLine("Main thread does some work, then waits.")
t.Join()
Console.WriteLine("Independent task has completed; main thread ends.")
End Sub
' The callback method must match the signature of the
' callback delegate.
'
Public Shared Sub ResultCallback(ByVal lineCount As Integer)
Console.WriteLine("Independent task printed {0} lines.", lineCount)
End Sub
End Class
[C#]
using System;
using System.Threading;
// The ThreadWithState class contains the information needed for
// a task, the method that executes the task, and a delegate
// to call when the task is complete.
//
public class ThreadWithState {
// State information used in the task.
private string boilerplate;
private int value;
// Delegate used to execute the callback method when the
// task is complete.
private ExampleCallback callback;
// The constructor obtains the state information and the
// callback delegate.
public ThreadWithState(string text, int number,
ExampleCallback callbackDelegate)
{
boilerplate = text;
value = number;
callback = callbackDelegate;
}
// The thread procedure performs the task, such as
// formatting and printing a document, and then invokes
// the callback delegate with the number of lines printed.
public void ThreadProc() {
Console.WriteLine(boilerplate, value);
if (callback != null)
callback(1);
}
}
// Delegate that defines the signature for the callback method.
//
public delegate void ExampleCallback(int lineCount);
// Entry point for the example.
//
public class Example {
public static void Main() {
// Supply the state information required by the task.
ThreadWithState tws = new ThreadWithState(
"This report displays the number {0}.",
42,
new ExampleCallback(ResultCallback)
);
Thread t = new Thread(new ThreadStart(tws.ThreadProc));
t.Start();
Console.WriteLine("Main thread does some work, then waits.");
t.Join();
Console.WriteLine("Independent task has completed; main thread ends.");
}
// The callback method must match the signature of the
// callback delegate.
//
public static void ResultCallback(int lineCount) {
Console.WriteLine("Independent task printed {0} lines.", lineCount);
}
}