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c#resetautoresetevent
anth
anth

Reputation: 1904

AutoResetEvent Reset method

Could someone introduce an use case for AutoResetEvent.Reset() method ? When and why I would like to use this method ? I understand WaitOne and Set but this is quite unclear for me.

Upvotes: 21

Views: 8309

Answers (6)

John Zhu
John Zhu

Reputation: 1099

Reset:

Sets the state of the event to nonsignaled ,See EventWaitHandle Class

Sample,

using System;
using System.Threading;
namespace ThreadingInCSharp.Signaling
{
    class Program
    {
        static EventWaitHandle _waitHandle = new AutoResetEvent(false);
        static void Main(string[] args)
        {
            //The event's state is Signal
            _waitHandle.Set();
            new Thread(Waiter).Start();
            Thread.Sleep(2000);
            _waitHandle.Set();
            Console.ReadKey();
        }
        private static void Waiter()
        {
            Console.WriteLine("I'm Waiting...");
            _waitHandle.WaitOne();
            //The word pass will print immediately 
            Console.WriteLine("pass");
        }
    }
}

Using Reset,

using System;
using System.Threading;
namespace ThreadingInCSharp.Signaling
{
    class Program
    {
        static EventWaitHandle _waitHandle = new AutoResetEvent(false);
        static void Main(string[] args)
        {
            //The event's state is Signal
            _waitHandle.Set();
            _waitHandle.Reset();
            new Thread(Waiter).Start();
            Thread.Sleep(2000);
            _waitHandle.Set();
            Console.ReadKey();
        }

        private static void Waiter()
        {
            Console.WriteLine("I'm Waiting...");
            _waitHandle.WaitOne();
            //The word will wait 2 seconds for printing
            Console.WriteLine("pass");
        }
    }
}

Upvotes: 1

JaredPar
JaredPar

Reputation: 754893

Yes the AutoResetEvent will automatically reset it's state whenever a thread which is waiting on the event is signaled. However it's possible that a given event is no longer valid and no thread has waited on an AutoResetEvent since it was originally set. In that scenario the Reset method becomes useful

Upvotes: 10

seairth
seairth

Reputation: 2062

If the AutoResetEvent producer wants to clear the event, you would use Reset(). This way, you can safely "reset" the event without having to know if it's currently signaled. If the producer used WaitOne to "reset" it's own event, there is a risk that you could deadlock (i.e. never return since the event isn't signaled and the producer thread is blocked).

Upvotes: 1

Dan Puzey
Dan Puzey

Reputation: 34198

The method is inherited from the base class EventWaitHandle and is used to (re)set an AutoResetEvent to its "blocked" state.

Because AutoResetEvent will automatically enter that state as soon as it's signalled, you'll typically never see this method used in code, but for other classes deriving from EventWaitHandle it would be much more useful!

Upvotes: 1

Tony The Lion
Tony The Lion

Reputation: 63220

You should use ManualResetEvent when using Reset(), as AutoResetEvent resets itself when a thread has become signaled.

Upvotes: 0

Svish
Svish

Reputation: 158091

Looks like it's just inherited from EventWaitHandle. Probably more useful with the ManualResetEvent which also inherits from that class?

Upvotes: 1

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