AsyncResult Class

 

Encapsulates the results of an asynchronous operation on a delegate.

Namespace:   System.Runtime.Remoting.Messaging
Assembly:  mscorlib (in mscorlib.dll)

System::Object
  System.Runtime.Remoting.Messaging::AsyncResult

[ComVisibleAttribute(true)]
public ref class AsyncResult : IAsyncResult, IMessageSink

NameDescription
System_CAPS_pubpropertyAsyncDelegate

Gets the delegate object on which the asynchronous call was invoked.

System_CAPS_pubpropertyAsyncState

Gets the object provided as the last parameter of a BeginInvoke method call.

System_CAPS_pubpropertyAsyncWaitHandle

Gets a WaitHandle that encapsulates Win32 synchronization handles, and allows the implementation of various synchronization schemes.

System_CAPS_pubpropertyCompletedSynchronously

Gets a value indicating whether the BeginInvoke call completed synchronously.

System_CAPS_pubpropertyEndInvokeCalled

Gets or sets a value indicating whether EndInvoke has been called on the current AsyncResult.

System_CAPS_pubpropertyIsCompleted

Gets a value indicating whether the server has completed the call.

System_CAPS_pubpropertyNextSink

Gets the next message sink in the sink chain.

NameDescription
System_CAPS_pubmethodAsyncProcessMessage(IMessage^, IMessageSink^)

Implements the IMessageSink interface.

System_CAPS_pubmethodEquals(Object^)

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

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetHashCode()

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

System_CAPS_pubmethodGetReplyMessage()

Gets the response message for the asynchronous call.

System_CAPS_pubmethodGetType()

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

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodSetMessageCtrl(IMessageCtrl^)

Sets an IMessageCtrl for the current remote method call, which provides a way to control asynchronous messages after they have been dispatched.

System_CAPS_pubmethodSyncProcessMessage(IMessage^)

Synchronously processes a response message returned by a method call on a remote object.

System_CAPS_pubmethodToString()

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

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.

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.

using namespace System;
using namespace System::Threading;
using namespace System::Runtime::InteropServices; 

namespace Examples {
namespace AdvancedProgramming {
namespace AsynchronousOperations
{
    public ref class AsyncDemo 
    {
    public:
        // The method to be executed asynchronously.
        String^ TestMethod(int callDuration, [OutAttribute] int% threadId) 
        {
            Console::WriteLine("Test method begins.");
            Thread::Sleep(callDuration);
            threadId = Thread::CurrentThread->ManagedThreadId;
            return String::Format("My call time was {0}.", callDuration);
        }
    };

    // The delegate must have the same signature as the method
    // it will call asynchronously.
    public delegate String^ AsyncMethodCaller(int callDuration, [OutAttribute] int% threadId);
}}}
#using <TestMethod.dll>

using namespace System;
using namespace System::Threading;
using namespace Examples::AdvancedProgramming::AsynchronousOperations;

void main() 
{
    // The asynchronous method puts the thread id here.
    int threadId;

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

    // Create the delegate.
    AsyncMethodCaller^ caller = gcnew AsyncMethodCaller(ad, &AsyncDemo::TestMethod);

    // Initiate the asychronous call.
    IAsyncResult^ result = caller->BeginInvoke(3000, 
        threadId, nullptr, nullptr);

    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(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.".
 */

.NET Framework
Available since 1.1

Any public static ( Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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