EventWaitHandle クラス
メモ : このクラスは、.NET Framework version 2.0 で新しく追加されたものです。
スレッドの同期イベントを表します。
名前空間: System.Threading
アセンブリ: mscorlib (mscorlib.dll 内)
構文
解説
使用例
継承階層
スレッド セーフ
プラットフォーム
バージョン情報
参照
アセンブリ: mscorlib (mscorlib.dll 内)
構文解説.gif) メモ |
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| このクラスに適用される HostProtectionAttribute 属性の Resources プロパティの値は、Synchronization または ExternalThreading です。HostProtectionAttribute は、デスクトップ アプリケーション (一般的には、アイコンをダブルクリック、コマンドを入力、またはブラウザに URL を入力して起動するアプリケーション) には影響しません。詳細については、HostProtectionAttribute クラスのトピックまたは「SQL Server プログラミングとホスト保護属性」を参照してください。 |
EventWaitHandle クラスを使用すると、スレッドはシグナルを通じて相互に通信できます。通常、EventWaitHandle では、ブロックされていないスレッドが Set メソッドを呼び出して 1 つ以上のブロックされたスレッドを解放するまでの間、1 つ以上のスレッドがブロックされます。スレッドは、static (Visual Basic では Shared) のSystem.Threading.WaitHandle.SignalAndWait メソッドを呼び出すことにより、分割不可能な操作として、EventWaitHandle にシグナルを通知してからブロックされます。
シグナル状態になった EventWaitHandle の動作は、リセット モードに依存します。EventResetMode.AutoReset フラグを指定して作成された EventWaitHandle がシグナル状態になっている場合は、待機中のスレッドを 1 つ解放した後で自動的にリセットされます。EventResetMode.ManualReset フラグを指定して作成された EventWaitHandle がシグナル状態になっている場合は、対応する Reset メソッドが呼び出されるまでシグナル状態のままとなります。
自動リセット イベントは、リソースへの排他的なアクセスを提供します。待機しているスレッドがないときに自動リセット イベントがシグナル状態になっている場合は、1 つのスレッドが待機を試みるまでシグナル状態のままとなります。このイベントはスレッドを解放した直後にリセットされ、後続のスレッドをブロックします。
手動リセットはゲートのようなものです。イベントがシグナル状態でないときは、イベントを待機しているスレッドはブロックされます。イベントがシグナル状態になっているときは、待機中のすべてのスレッドが解放され、対応する Reset メソッドが呼び出されるまでイベントがシグナル状態のままになります (つまり、後続の待機スレッドはブロックされません)。手動リセット イベントは、1 つのスレッドが処理を完了しないと他のスレッドが続行できない場合に便利です。
EventWaitHandle オブジェクトは、static (Visual Basic では Shared) の System.Threading.WaitHandle.WaitAll メソッドおよび System.Threading.WaitHandle.WaitAny メソッドと組み合わせても使用できます。
スレッドの同期機構の詳細については、「EventWaitHandle、AutoResetEvent、および ManualResetEvent」を参照してください。
使用例SignalAndWait(WaitHandle,WaitHandle) メソッド オーバーロードを使用して、メイン スレッドがブロックされているスレッドにシグナルを送信し、そのスレッドがタスクを完了するまで待機できるようにするコード例を次に示します。
この例では 5 つのスレッドを起動し、それらのスレッドを EventResetMode.AutoReset フラグを指定して作成された EventWaitHandle でブロックした後、ユーザーが Enter キーを押すたびにスレッドが 1 つずつ解放されるようにします。次に、別の 5 つのスレッドをキューに置き、EventResetMode.ManualReset フラグを指定して作成された EventWaitHandle を使用して、これらのスレッドをすべて解放します。
Imports System Imports System.Threading Public Class Example ' The EventWaitHandle used to demonstrate the difference ' between AutoReset and ManualReset synchronization events. ' Private Shared ewh As EventWaitHandle ' A counter to make sure all threads are started and ' blocked before any are released. A Long is used to show ' the use of the 64-bit Interlocked methods. ' Private Shared threadCount As Long = 0 ' An AutoReset event that allows the main thread to block ' until an exiting thread has decremented the count. ' Private Shared clearCount As New EventWaitHandle(False, _ EventResetMode.AutoReset) <MTAThread> _ Public Shared Sub Main() ' Create an AutoReset EventWaitHandle. ' ewh = New EventWaitHandle(False, EventResetMode.AutoReset) ' Create and start five numbered threads. Use the ' ParameterizedThreadStart delegate, so the thread ' number can be passed as an argument to the Start ' method. For i As Integer = 0 To 4 Dim t As New Thread(AddressOf ThreadProc) t.Start(i) Next i ' Wait until all the threads have started and blocked. ' When multiple threads use a 64-bit value on a 32-bit ' system, you must access the value through the ' Interlocked class to guarantee thread safety. ' While Interlocked.Read(threadCount) < 5 Thread.Sleep(500) End While ' Release one thread each time the user presses ENTER, ' until all threads have been released. ' While Interlocked.Read(threadCount) > 0 Console.WriteLine("Press ENTER to release a waiting thread.") Console.ReadLine() ' SignalAndWait signals the EventWaitHandle, which ' releases exactly one thread before resetting, ' because it was created with AutoReset mode. ' SignalAndWait then blocks on clearCount, to ' allow the signaled thread to decrement the count ' before looping again. ' WaitHandle.SignalAndWait(ewh, clearCount) End While Console.WriteLine() ' Create a ManualReset EventWaitHandle. ' ewh = New EventWaitHandle(False, EventResetMode.ManualReset) ' Create and start five more numbered threads. ' For i As Integer = 0 To 4 Dim t As New Thread(AddressOf ThreadProc) t.Start(i) Next i ' Wait until all the threads have started and blocked. ' While Interlocked.Read(threadCount) < 5 Thread.Sleep(500) End While ' Because the EventWaitHandle was created with ' ManualReset mode, signaling it releases all the ' waiting threads. ' Console.WriteLine("Press ENTER to release the waiting threads.") Console.ReadLine() ewh.Set() End Sub Public Shared Sub ThreadProc(ByVal data As Object) Dim index As Integer = CInt(data) Console.WriteLine("Thread {0} blocks.", data) ' Increment the count of blocked threads. Interlocked.Increment(threadCount) ' Wait on the EventWaitHandle. ewh.WaitOne() Console.WriteLine("Thread {0} exits.", data) ' Decrement the count of blocked threads. Interlocked.Decrement(threadCount) ' After signaling ewh, the main thread blocks on ' clearCount until the signaled thread has ' decremented the count. Signal it now. ' clearCount.Set() End Sub End Class
using System; using System.Threading; public class Example { // The EventWaitHandle used to demonstrate the difference // between AutoReset and ManualReset synchronization events. // private static EventWaitHandle ewh; // A counter to make sure all threads are started and // blocked before any are released. A Long is used to show // the use of the 64-bit Interlocked methods. // private static long threadCount = 0; // An AutoReset event that allows the main thread to block // until an exiting thread has decremented the count. // private static EventWaitHandle clearCount = new EventWaitHandle(false, EventResetMode.AutoReset); [MTAThread] public static void Main() { // Create an AutoReset EventWaitHandle. // ewh = new EventWaitHandle(false, EventResetMode.AutoReset); // Create and start five numbered threads. Use the // ParameterizedThreadStart delegate, so the thread // number can be passed as an argument to the Start // method. for (int i = 0; i <= 4; i++) { Thread t = new Thread( new ParameterizedThreadStart(ThreadProc) ); t.Start(i); } // Wait until all the threads have started and blocked. // When multiple threads use a 64-bit value on a 32-bit // system, you must access the value through the // Interlocked class to guarantee thread safety. // while (Interlocked.Read(ref threadCount) < 5) { Thread.Sleep(500); } // Release one thread each time the user presses ENTER, // until all threads have been released. // while (Interlocked.Read(ref threadCount) > 0) { Console.WriteLine("Press ENTER to release a waiting thread."); Console.ReadLine(); // SignalAndWait signals the EventWaitHandle, which // releases exactly one thread before resetting, // because it was created with AutoReset mode. // SignalAndWait then blocks on clearCount, to // allow the signaled thread to decrement the count // before looping again. // WaitHandle.SignalAndWait(ewh, clearCount); } Console.WriteLine(); // Create a ManualReset EventWaitHandle. // ewh = new EventWaitHandle(false, EventResetMode.ManualReset); // Create and start five more numbered threads. // for(int i=0; i<=4; i++) { Thread t = new Thread( new ParameterizedThreadStart(ThreadProc) ); t.Start(i); } // Wait until all the threads have started and blocked. // while (Interlocked.Read(ref threadCount) < 5) { Thread.Sleep(500); } // Because the EventWaitHandle was created with // ManualReset mode, signaling it releases all the // waiting threads. // Console.WriteLine("Press ENTER to release the waiting threads."); Console.ReadLine(); ewh.Set(); } public static void ThreadProc(object data) { int index = (int) data; Console.WriteLine("Thread {0} blocks.", data); // Increment the count of blocked threads. Interlocked.Increment(ref threadCount); // Wait on the EventWaitHandle. ewh.WaitOne(); Console.WriteLine("Thread {0} exits.", data); // Decrement the count of blocked threads. Interlocked.Decrement(ref threadCount); // After signaling ewh, the main thread blocks on // clearCount until the signaled thread has // decremented the count. Signal it now. // clearCount.Set(); } }
using namespace System; using namespace System::Threading; public ref class Example { private: // The EventWaitHandle used to demonstrate the difference // between AutoReset and ManualReset synchronization events. // static EventWaitHandle^ ewh; // A counter to make sure all threads are started and // blocked before any are released. A Long is used to show // the use of the 64-bit Interlocked methods. // static __int64 threadCount = 0; // An AutoReset event that allows the main thread to block // until an exiting thread has decremented the count. // static EventWaitHandle^ clearCount = gcnew EventWaitHandle( false,EventResetMode::AutoReset ); public: [MTAThread] static void main() { // Create an AutoReset EventWaitHandle. // ewh = gcnew EventWaitHandle( false,EventResetMode::AutoReset ); // Create and start five numbered threads. Use the // ParameterizedThreadStart delegate, so the thread // number can be passed as an argument to the Start // method. for ( int i = 0; i <= 4; i++ ) { Thread^ t = gcnew Thread( gcnew ParameterizedThreadStart( ThreadProc ) ); t->Start( i ); } // Wait until all the threads have started and blocked. // When multiple threads use a 64-bit value on a 32-bit // system, you must access the value through the // Interlocked class to guarantee thread safety. // while ( Interlocked::Read( threadCount ) < 5 ) { Thread::Sleep( 500 ); } // Release one thread each time the user presses ENTER, // until all threads have been released. // while ( Interlocked::Read( threadCount ) > 0 ) { Console::WriteLine( L"Press ENTER to release a waiting thread." ); Console::ReadLine(); // SignalAndWait signals the EventWaitHandle, which // releases exactly one thread before resetting, // because it was created with AutoReset mode. // SignalAndWait then blocks on clearCount, to // allow the signaled thread to decrement the count // before looping again. // WaitHandle::SignalAndWait( ewh, clearCount ); } Console::WriteLine(); // Create a ManualReset EventWaitHandle. // ewh = gcnew EventWaitHandle( false,EventResetMode::ManualReset ); // Create and start five more numbered threads. // for ( int i = 0; i <= 4; i++ ) { Thread^ t = gcnew Thread( gcnew ParameterizedThreadStart( ThreadProc ) ); t->Start( i ); } // Wait until all the threads have started and blocked. // while ( Interlocked::Read( threadCount ) < 5 ) { Thread::Sleep( 500 ); } // Because the EventWaitHandle was created with // ManualReset mode, signaling it releases all the // waiting threads. // Console::WriteLine( L"Press ENTER to release the waiting threads." ); Console::ReadLine(); ewh->Set(); } static void ThreadProc( Object^ data ) { int index = static_cast<Int32>(data); Console::WriteLine( L"Thread {0} blocks.", data ); // Increment the count of blocked threads. Interlocked::Increment( threadCount ); // Wait on the EventWaitHandle. ewh->WaitOne(); Console::WriteLine( L"Thread {0} exits.", data ); // Decrement the count of blocked threads. Interlocked::Decrement( threadCount ); // After signaling ewh, the main thread blocks on // clearCount until the signaled thread has // decremented the count. Signal it now. // clearCount->Set(); } };
import System.*; import System.Threading.*; public class Example { // The EventWaitHandle used to demonstrate the difference // between AutoReset and ManualReset synchronization events. // private static EventWaitHandle ewh; // A counter to make sure all threads are started and // blocked before any are released. A Long is used to show // the use of the 64-bit Interlocked methods. // private static long threadCount = 0; // An AutoReset event that allows the main thread to block // until an exiting thread has decremented the count. // private static EventWaitHandle clearCount = new EventWaitHandle(false, EventResetMode.AutoReset); /** @attribute MTAThread() */ public static void main(String[] args) { // Create an AutoReset EventWaitHandle. // ewh = new EventWaitHandle(false, EventResetMode.AutoReset); // Create and start five numbered threads. Use the // ParameterizedThreadStart delegate, so the thread // number can be passed as an argument to the Start // method. for (int i = 0; i <= 4; i++) { System.Threading.Thread t = new System.Threading.Thread(new ParameterizedThreadStart(ThreadProc)); t.Start((Int32)i); } // Wait until all the threads have started and blocked. // When multiple threads use a 64-bit value on a 32-bit // system, you must access the value through the // Interlocked class to guarantee thread safety. // while (Interlocked.Read(threadCount) < 5) { System.Threading.Thread.Sleep(500); } // Release one thread each time the user presses ENTER, // until all threads have been released. // while (Interlocked.Read(threadCount) > 0) { Console.WriteLine("Press ENTER to release a waiting thread."); Console.ReadLine(); // SignalAndWait signals the EventWaitHandle, which // releases exactly one thread before resetting, // because it was created with AutoReset mode. // SignalAndWait then blocks on clearCount, to // allow the signaled thread to decrement the count // before looping again. // WaitHandle.SignalAndWait(ewh, clearCount); } Console.WriteLine(); // Create a ManualReset EventWaitHandle. // ewh = new EventWaitHandle(false, EventResetMode.ManualReset); // Create and start five more numbered threads. // for (int i = 0; i <= 4; i++) { System.Threading.Thread t = new System.Threading.Thread(new ParameterizedThreadStart(ThreadProc)); t.Start((Int32)i); } // Wait until all the threads have started and blocked. // while (Interlocked.Read(threadCount) < 5) { System.Threading.Thread.Sleep(500); } // Because the EventWaitHandle was created with // ManualReset mode, signaling it releases all the // waiting threads. // Console.WriteLine("Press ENTER to release the waiting threads."); Console.ReadLine(); ewh.Set(); } //main public static void ThreadProc(Object data) { int index = System.Convert.ToInt32(data); Console.WriteLine("Thread {0} blocks.", data); // Increment the count of blocked threads. Interlocked.Increment(threadCount); // Wait on the EventWaitHandle. ewh.WaitOne(); Console.WriteLine("Thread {0} exits.", data); // Decrement the count of blocked threads. Interlocked.Decrement(threadCount); // After signaling ewh, the main thread blocks on // clearCount until the signaled thread has // decremented the count. Signal it now. // clearCount.Set(); } //ThreadProc } //Example
継承階層
System.Object
System.MarshalByRefObject
System.Threading.WaitHandle
System.Threading.EventWaitHandle
System.Threading.AutoResetEvent
System.Threading.ManualResetEvent
System.MarshalByRefObject
System.Threading.WaitHandle
System.Threading.EventWaitHandle
System.Threading.AutoResetEvent
System.Threading.ManualResetEvent
スレッド セーフプラットフォームWindows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。
バージョン情報参照- EventWaitHandle クラスのページへのリンク
