ManualResetEvent Class

 

Notifies one or more waiting threads that an event has occurred. This class cannot be inherited.

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

System.Object
  System.MarshalByRefObject
    System.Threading.WaitHandle
      System.Threading.EventWaitHandle
        System.Threading.ManualResetEvent

[ComVisibleAttribute(true)]
[HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true, 
	ExternalThreading = true)]
public sealed class ManualResetEvent : EventWaitHandle

NameDescription
System_CAPS_pubmethodManualResetEvent(Boolean)

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

NameDescription
System_CAPS_pubpropertyHandle

Obsolete.Gets or sets the native operating system handle.(Inherited from WaitHandle.)

System_CAPS_pubpropertySafeWaitHandle

Gets or sets the native operating system handle.(Inherited from WaitHandle.)

NameDescription
System_CAPS_pubmethodClose()

Releases all resources held by the current WaitHandle.(Inherited from WaitHandle.)

System_CAPS_pubmethodCreateObjRef(Type)

Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object.(Inherited from MarshalByRefObject.)

System_CAPS_pubmethodDispose()

Releases all resources used by the current instance of the WaitHandle class.(Inherited from WaitHandle.)

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_pubmethodGetAccessControl()

Gets an EventWaitHandleSecurity object that represents the access control security for the named system event represented by the current EventWaitHandle object.(Inherited from EventWaitHandle.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetLifetimeService()

Retrieves the current lifetime service object that controls the lifetime policy for this instance.(Inherited from MarshalByRefObject.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethodInitializeLifetimeService()

Obtains a lifetime service object to control the lifetime policy for this instance.(Inherited from MarshalByRefObject.)

System_CAPS_pubmethodReset()

Sets the state of the event to nonsignaled, causing threads to block.(Inherited from EventWaitHandle.)

System_CAPS_pubmethodSet()

Sets the state of the event to signaled, allowing one or more waiting threads to proceed.(Inherited from EventWaitHandle.)

System_CAPS_pubmethodSetAccessControl(EventWaitHandleSecurity)

Sets the access control security for a named system event.(Inherited from EventWaitHandle.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

System_CAPS_pubmethodWaitOne()

Blocks the current thread until the current WaitHandle receives a signal.(Inherited from WaitHandle.)

System_CAPS_pubmethodWaitOne(Int32)

Blocks the current thread until the current WaitHandle receives a signal, using a 32-bit signed integer to specify the time interval in milliseconds.(Inherited from WaitHandle.)

System_CAPS_pubmethodWaitOne(Int32, Boolean)

Blocks the current thread until the current WaitHandle receives a signal, using a 32-bit signed integer to specify the time interval and specifying whether to exit the synchronization domain before the wait.(Inherited from WaitHandle.)

System_CAPS_pubmethodWaitOne(TimeSpan)

Blocks the current thread until the current instance receives a signal, using a TimeSpan to specify the time interval.(Inherited from WaitHandle.)

System_CAPS_pubmethodWaitOne(TimeSpan, Boolean)

Blocks the current thread until the current instance receives a signal, using a TimeSpan to specify the time interval and specifying whether to exit the synchronization domain before the wait.(Inherited from WaitHandle.)

NameDescription
System_CAPS_pubmethodGetSafeWaitHandle()

Gets the safe handle for a native operating system wait handle. (Defined by WaitHandleExtensions.)

System_CAPS_pubmethodSetSafeWaitHandle(SafeWaitHandle)

Sets a safe handle for a native operating system wait handle. (Defined by WaitHandleExtensions.)

In the .NET Framework version 2.0, ManualResetEvent derives from the new EventWaitHandle class. A ManualResetEvent is functionally equivalent to an EventWaitHandle created with EventResetMode.ManualReset.

System_CAPS_noteNote

Unlike the ManualResetEvent class, the EventWaitHandle class provides access to named system synchronization events.

ManualResetEvent allows threads to communicate with each other by signaling. Typically, this communication concerns a task which one thread must complete before other threads can proceed.

When a thread begins an activity that must complete before other threads proceed, it calls Reset to put ManualResetEvent in the non-signaled state. This thread can be thought of as controlling the ManualResetEvent. Threads that call WaitOne on the ManualResetEvent will block, awaiting the signal. When the controlling thread completes the activity, it calls Set to signal that the waiting threads can proceed. All waiting threads are released.

Once it has been signaled, ManualResetEvent remains signaled until it is manually reset. That is, calls to WaitOne return immediately.

You can control the initial state of a ManualResetEvent by passing a Boolean value to the constructor, true if the initial state is signaled and false otherwise.

ManualResetEvent can also be used with the staticWaitAll and WaitAny methods.

For more information about thread synchronization mechanisms, see ManualResetEvent and ManualResetEventSlim in the conceptual documentation.

The following example demonstrates how ManualResetEvent works. The example starts with a ManualResetEvent in the unsignaled state (that is, false is passed to the constructor). The example creates three threads, each of which blocks on the ManualResetEvent by calling its WaitOne method. When the user presses the Enter key, the example calls the Set method, which releases all three threads. Contrast this with the behavior of the AutoResetEvent class, which releases threads one at a time, resetting automatically after each release.

Pressing the Enter key again demonstrates that the ManualResetEvent remains in the signaled state until its Reset method is called: The example starts two more threads. These threads do not block when they call the WaitOne method, but instead run to completion.

Pressing the Enter key again causes the example to call the Reset method and to start one more thread, which blocks when it calls WaitOne. Pressing the Enter key one final time calls Set to release the last thread, and the program ends.

using System;
using System.Threading;

public class Example
{
    // mre is used to block and release threads manually. It is
    // created in the unsignaled state.
    private static ManualResetEvent mre = new ManualResetEvent(false);

    static void Main()
    {
        Console.WriteLine("\nStart 3 named threads that block on a ManualResetEvent:\n");

        for(int i = 0; i <= 2; i++)
        {
            Thread t = new Thread(ThreadProc);
            t.Name = "Thread_" + i;
            t.Start();
        }

        Thread.Sleep(500);
        Console.WriteLine("\nWhen all three threads have started, press Enter to call Set()" +
                          "\nto release all the threads.\n");
        Console.ReadLine();

        mre.Set();

        Thread.Sleep(500);
        Console.WriteLine("\nWhen a ManualResetEvent is signaled, threads that call WaitOne()" +
                          "\ndo not block. Press Enter to show this.\n");
        Console.ReadLine();

        for(int i = 3; i <= 4; i++)
        {
            Thread t = new Thread(ThreadProc);
            t.Name = "Thread_" + i;
            t.Start();
        }

        Thread.Sleep(500);
        Console.WriteLine("\nPress Enter to call Reset(), so that threads once again block" +
                          "\nwhen they call WaitOne().\n");
        Console.ReadLine();

        mre.Reset();

        // Start a thread that waits on the ManualResetEvent.
        Thread t5 = new Thread(ThreadProc);
        t5.Name = "Thread_5";
        t5.Start();

        Thread.Sleep(500);
        Console.WriteLine("\nPress Enter to call Set() and conclude the demo.");
        Console.ReadLine();

        mre.Set();

        // If you run this example in Visual Studio, uncomment the following line:
        //Console.ReadLine();
    }


    private static void ThreadProc()
    {
        string name = Thread.CurrentThread.Name;

        Console.WriteLine(name + " starts and calls mre.WaitOne()");

        mre.WaitOne();

        Console.WriteLine(name + " ends.");
    }
}

/* This example produces output similar to the following:

Start 3 named threads that block on a ManualResetEvent:

Thread_0 starts and calls mre.WaitOne()
Thread_1 starts and calls mre.WaitOne()
Thread_2 starts and calls mre.WaitOne()

When all three threads have started, press Enter to call Set()
to release all the threads.


Thread_2 ends.
Thread_0 ends.
Thread_1 ends.

When a ManualResetEvent is signaled, threads that call WaitOne()
do not block. Press Enter to show this.


Thread_3 starts and calls mre.WaitOne()
Thread_3 ends.
Thread_4 starts and calls mre.WaitOne()
Thread_4 ends.

Press Enter to call Reset(), so that threads once again block
when they call WaitOne().


Thread_5 starts and calls mre.WaitOne()

Press Enter to call Set() and conclude the demo.

Thread_5 ends.
 */

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1

This class is thread safe.

Return to top
Show: