AutoResetEvent Constructor

The following example uses an AutoResetEvent to synchronize the activities of two threads. The first thread, which is the application thread, executes Main. It writes values to the protected resource, which is a static (Shared in Visual Basic) field named number. The second thread executes the static ThreadProc method, which reads the values written by Main.

The ThreadProc method waits for the AutoResetEvent. When Main calls the Set method on the AutoResetEvent, the ThreadProc method reads one value. The AutoResetEvent immediately resets, so the ThreadProc method waits again.

The program logic guarantees that the ThreadProc method will never read the same value two times. It does not guarantee that the ThreadProc method will read every value written by Main. That guarantee would require a second AutoResetEvent lock.

After each write operation, Main yields by calling the Thread::Sleep method, to give the second thread a chance to execute. Otherwise, on a single-processor computer Main would write many values between any two read operations.

using namespace System;
using namespace System::Threading;
ref class MyMainClass
{
public:
   static void MyReadThreadProc()
   {
      while ( true )
      {

         //The value will not be read until the writer has written 
         // at least once since the last read.
         myResetEvent->WaitOne();
         Console::WriteLine( " {0} reading value: {1}", Thread::CurrentThread->Name, number );
      }
   }


   //Initially not signaled. 
   static AutoResetEvent^ myResetEvent = gcnew AutoResetEvent( false );
   static int number;
   literal int numIterations = 100;
};

int main()
{

   //Create and start the reader thread.
   Thread^ myReaderThread = gcnew Thread( gcnew ThreadStart( MyMainClass::MyReadThreadProc ) );
   myReaderThread->Name = "ReaderThread";
   myReaderThread->Start();
   for ( int i = 1; i <= MyMainClass::numIterations; i++ )
   {
      Console::WriteLine( "Writer thread writing value: {0}", i );
      MyMainClass::number = i;

      //Signal that a value has been written.
      MyMainClass::myResetEvent->Set();

      //Give the Reader thread an opportunity to act.
      Thread::Sleep( 1 );

   }

   //Terminate the reader thread.
   myReaderThread->Abort();
}

.NET Framework

.NET Framework Client Profile

Portable Class Library

.NET for Windows Store apps

Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Reference

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