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AutoResetEvent.AutoResetEvent Constructor

Initializes a new instance of the AutoResetEvent class with a Boolean value indicating whether to set the initial state to signaled.

Namespace: System.Threading
Assembly: mscorlib (in mscorlib.dll)

public AutoResetEvent (
	bool initialState
)
public AutoResetEvent (
	boolean initialState
)
public function AutoResetEvent (
	initialState : boolean
)
Not applicable.

Parameters

initialState

true to set the initial state to signaled; false to set the initial state to non-signaled.

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 System;
using System.Threading;

namespace AutoResetEvent_Examples
{
	class MyMainClass
	{
		//Initially not signaled.
      const int numIterations = 100;
      static AutoResetEvent myResetEvent = new AutoResetEvent(false);
      static int number;
      
      static void Main()
		{
         //Create and start the reader thread.
         Thread myReaderThread = new Thread(new ThreadStart(MyReadThreadProc));
         myReaderThread.Name = "ReaderThread";
         myReaderThread.Start();

         for(int i = 1; i <= numIterations; i++)
         {
            Console.WriteLine("Writer thread writing value: {0}", i);
            number = i;
            
            //Signal that a value has been written.
            myResetEvent.Set();
            
            //Give the Reader thread an opportunity to act.
            Thread.Sleep(0);
         }

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

      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);
         }
      }
	}
}

package AutoResetEvent_Examples;

import System.*;
import System.Threading.*;
import System.Threading.Thread;

class MyMainClass
{
    //Initially not signaled.
    private final static int numIterations = 100;
    private static AutoResetEvent myResetEvent = new AutoResetEvent(false);
    private static int number;

    public static void main(String[] args)
    {
        //Create and start the reader thread.
        Thread myReaderThread = new Thread(new ThreadStart(MyReadThreadProc));
        myReaderThread.set_Name("ReaderThread");
        myReaderThread.Start();
        for (int i = 1; i <= numIterations; i++) {
            Console.WriteLine("Writer thread writing value: {0}",
                String.valueOf(i));
            number = i;

            //Signal that a value has been written.
            myResetEvent.Set();

            //Give the Reader thread an opportunity to act.
            Thread.Sleep(0);
        }

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

    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.get_CurrentThread().get_Name(),String.valueOf(number));
        }
    } //MyReadThreadProc
} //MyMainClass

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0
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