AsyncResult Class
Assembly: mscorlib (in mscorlib.dll)
'Declaration <ComVisibleAttribute(True)> _ Public Class AsyncResult Implements IAsyncResult, IMessageSink 'Usage Dim instance As AsyncResult
/** @attribute ComVisibleAttribute(true) */ public class AsyncResult implements IAsyncResult, IMessageSink
ComVisibleAttribute(true) public class AsyncResult implements IAsyncResult, IMessageSink
The AsyncResult class is used in conjunction with asynchronous 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 async call was invoked.
For more information about BeginInvoke and asynchronous delegates, see Asynchronous Programming Using Delegates.
The following code example demonstrates the use of the AsyncResult class to retrieve the results of an asynchronous operation on an asynchronous delegate.
Imports System Imports System.Threading Imports System.Runtime.Remoting Imports System.Runtime.Remoting.Contexts Imports System.Runtime.Remoting.Messaging ' Context-bound type with the Synchronization context attribute. <Synchronization()> Public Class SampleSyncronized Inherits ContextBoundObject ' A method that does some work, and returns the square of the given number. Public Function Square(i As Integer) As Integer Console.Write("The hash of the thread executing ") Console.WriteLine("SampleSyncronized.Square is: {0}", Thread.CurrentThread.GetHashCode()) Return i * i End Function 'Square End Class 'SampleSyncronized ' The async delegate used to call a method with this signature asynchronously. Delegate Function SampSyncSqrDelegate(i As Integer) As Integer Public Class AsyncResultSample ' Asynchronous Callback method. Public Shared Sub MyCallback(ar As IAsyncResult) ' Obtains the last parameter of the delegate call. Dim value As Integer = Convert.ToInt32(ar.AsyncState) ' Obtains return value from the delegate call using EndInvoke. Dim aResult As AsyncResult = CType(ar, AsyncResult) Dim temp As SampSyncSqrDelegate = CType(aResult.AsyncDelegate, SampSyncSqrDelegate) Dim result As Integer = temp.EndInvoke(ar) Console.Write("Simple.SomeMethod (AsyncCallback): Result of ") Console.WriteLine("{0} in SampleSynchronized.Square is {1} ", value, result) End Sub 'MyCallback Public Shared Sub Main() Dim result As Integer Dim param As Integer ' Creates an instance of a context-bound type SampleSynchronized. Dim sampSyncObj As New SampleSyncronized() ' Checks whether the object is a proxy, since it is context-bound. If RemotingServices.IsTransparentProxy(sampSyncObj) Then Console.WriteLine("sampSyncObj is a proxy.") Else Console.WriteLine("sampSyncObj is NOT a proxy.") End If param = 10 Console.WriteLine("") Console.WriteLine("Making a synchronous call on the context-bound object:") result = sampSyncObj.Square(param) Console.Write("The result of calling sampSyncObj.Square with ") Console.WriteLine("{0} is {1}.", param, result) Console.WriteLine("") Dim sampleDelegate As New SampSyncSqrDelegate(AddressOf sampSyncObj.Square) param = 8 Console.WriteLine("Making a single asynchronous call on the context-bound object:") Dim ar1 As IAsyncResult = sampleDelegate.BeginInvoke(param, New AsyncCallback(AddressOf AsyncResultSample.MyCallback), param) Console.WriteLine("Waiting for the asynchronous call to complete...") Dim wh As WaitHandle = ar1.AsyncWaitHandle wh.WaitOne() Console.WriteLine("") Console.WriteLine("Waiting for the AsyncCallback to complete...") Thread.Sleep(1000) End Sub 'Main End Class 'AsyncResultSample
import System.*;
import System.Threading.*;
import System.Runtime.Remoting.*;
import System.Runtime.Remoting.Contexts.*;
import System.Runtime.Remoting.Messaging.*;
// Context-bound type with the Synchronization context attribute.
/** @attribute Synchronization()
*/
public class SampleSyncronized extends ContextBoundObject
{
// A method that does some work, and returns the square of the given number.
public int Square(int i)
{
Console.Write("The hash of the thread executing ");
Console.WriteLine("SampleSyncronized.Square is: {0}",
(Int32)System.Threading.Thread.get_CurrentThread().GetHashCode());
return i * i;
} //Square
} //SampleSyncronized
// The async delegate used to call a method with this signature asynchronously.
/** @delegate
*/
public delegate int SampSyncSqrDelegate(int i);
public class AsyncResultSample
{
static int value;
// Asynchronous Callback method.
public static void MyCallback(IAsyncResult ar)
{
// Obtains the last parameter of the delegate call.
SampSyncSqrDelegate sampDelg = (SampSyncSqrDelegate)ar.get_AsyncState();
// Obtains return value from the delegate call using EndInvoke.
AsyncResult aResult = (AsyncResult)ar;
SampSyncSqrDelegate temp =
(SampSyncSqrDelegate)(aResult.get_AsyncDelegate());
int threadId = AppDomain.GetCurrentThreadId();
int result = temp.EndInvoke(ar);
Console.Write("Simple.SomeMethod (AsyncCallback): Result of ");
Console.WriteLine("{0} in SampleSynchronized.Square is {1} ",
(Int32)value, (Int32)result);
} //MyCallback
public static void main(String[] args)
{
int result;
int param;
// Creates an instance of a context-bound type SampleSynchronized.
SampleSyncronized sampSyncObj = new SampleSyncronized();
// Checks whether the object is a proxy, since it is context-bound.
if (RemotingServices.IsTransparentProxy(sampSyncObj)) {
Console.WriteLine("sampSyncObj is a proxy.");
}
else {
Console.WriteLine("sampSyncObj is NOT a proxy.");
}
param = 10;
Console.WriteLine("");
Console.WriteLine("Making a synchronous call on the context-bound "
+ "object:");
result = sampSyncObj.Square(param);
Console.Write("The result of calling sampSyncObj.Square with ");
Console.WriteLine("{0} is {1}.", (Int32)param, (Int32)result);
Console.WriteLine("");
SampSyncSqrDelegate sampleDelegate =
new SampSyncSqrDelegate(sampSyncObj.Square);
param = 8;
value = param;
Console.WriteLine("Making a single asynchronous call on the "
+ "context-bound object:");
IAsyncResult ar1 = sampleDelegate.BeginInvoke(param,
new AsyncCallback(AsyncResultSample.MyCallback), sampleDelegate);
Console.WriteLine("Waiting for the asynchronous call to complete...");
WaitHandle wh = ar1.get_AsyncWaitHandle();
wh.WaitOne();
Console.WriteLine("");
Console.WriteLine("Waiting for the AsyncCallback to complete...");
System.Threading.Thread.Sleep(1000);
} //main
} //AsyncResultSample
Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.