AsyncResult Class

Definition

Namespace:

System.Runtime.Remoting.Messaging

Assembly:

mscorlib.dll

Encapsulates the results of an asynchronous operation on a delegate.

C#

[System.Runtime.InteropServices.ComVisible(true)]
public class AsyncResult : IAsyncResult, System.Runtime.Remoting.Messaging.IMessageSink

Inheritance

Object

AsyncResult

Attributes

ComVisibleAttribute

Implements

IAsyncResult IMessageSink

Examples

The following example demonstrates how to use the AsyncWaitHandle property to get a WaitHandle, and how to wait for an asynchronous call on a delegate. The WaitHandle is signaled when the asynchronous call completes, and you can wait for it by calling the WaitOne method.

The example consists of two classes, the class that contains the method which is called asynchronously, and the class that contains the Main method that makes the call.

For more information and more examples of calling methods asynchronously by using delegates, see Calling Synchronous Methods Asynchronously.

C#

using System;
using System.Threading;

namespace Examples.AdvancedProgramming.AsynchronousOperations
{
    public class AsyncDemo
    {
        // The method to be executed asynchronously.
        public string TestMethod(int callDuration, out int threadId)
        {
            Console.WriteLine("Test method begins.");
            Thread.Sleep(callDuration);
            threadId = Thread.CurrentThread.ManagedThreadId;
            return String.Format("My call time was {0}.", callDuration.ToString());
        }
    }
    // The delegate must have the same signature as the method
    // it will call asynchronously.
    public delegate string AsyncMethodCaller(int callDuration, out int threadId);
}

C#

using System;
using System.Threading;

namespace Examples.AdvancedProgramming.AsynchronousOperations
{
    public class AsyncMain
    {
        static void Main()
        {
            // The asynchronous method puts the thread id here.
            int threadId;

            // Create an instance of the test class.
            AsyncDemo ad = new AsyncDemo();

            // Create the delegate.
            AsyncMethodCaller caller = new AsyncMethodCaller(ad.TestMethod);

            // Initiate the asychronous call.
            IAsyncResult result = caller.BeginInvoke(3000,
                out threadId, null, null);

            Thread.Sleep(0);
            Console.WriteLine("Main thread {0} does some work.",
                Thread.CurrentThread.ManagedThreadId);

            // Wait for the WaitHandle to become signaled.
            result.AsyncWaitHandle.WaitOne();

            // Perform additional processing here.
            // Call EndInvoke to retrieve the results.
            string returnValue = caller.EndInvoke(out threadId, result);

            // Close the wait handle.
            result.AsyncWaitHandle.Close();

            Console.WriteLine("The call executed on thread {0}, with return value \"{1}\".",
                threadId, returnValue);
        }
    }
}

/* This example produces output similar to the following:

Main thread 1 does some work.
Test method begins.
The call executed on thread 3, with return value "My call time was 3000.".
 */

Remarks

The AsyncResult class is used in conjunction with asynchronous method calls made using delegates. The IAsyncResult returned from the delegate's BeginInvoke method can be cast to an AsyncResult. The AsyncResult has the AsyncDelegate property that holds the delegate object on which the asynchronous call was invoked.

For more information about BeginInvoke and asynchronous calls using delegates, see Asynchronous Programming Using Delegates.

Properties

AsyncDelegate	Gets the delegate object on which the asynchronous call was invoked.
AsyncState	Gets the object provided as the last parameter of a BeginInvoke method call.
AsyncWaitHandle	Gets a WaitHandle that encapsulates Win32 synchronization handles, and allows the implementation of various synchronization schemes.
CompletedSynchronously	Gets a value indicating whether the BeginInvoke call completed synchronously.
EndInvokeCalled	Gets or sets a value indicating whether EndInvoke has been called on the current AsyncResult.
IsCompleted	Gets a value indicating whether the server has completed the call.
NextSink	Gets the next message sink in the sink chain.

Methods

AsyncProcessMessage(IMessage, IMessageSink)	Implements the IMessageSink interface.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetReplyMessage()	Gets the response message for the asynchronous call.
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
SetMessageCtrl(IMessageCtrl)	Sets an IMessageCtrl for the current remote method call, which provides a way to control asynchronous messages after they have been dispatched.
SyncProcessMessage(IMessage)	Synchronously processes a response message returned by a method call on a remote object.
ToString()	Returns a string that represents the current object. (Inherited from Object)

Applies to

See also

• Asynchronous Programming Using Delegates