Interfaccia IAsyncResult
Rappresenta lo stato di un'operazione asincrona.
Spazio dei nomi: System
Assembly: mscorlib (in mscorlib.dll)
Sintassi
'Dichiarazione
<ComVisibleAttribute(True)> _
Public Interface IAsyncResult
'Utilizzo
Dim instance As IAsyncResult
[ComVisibleAttribute(true)]
public interface IAsyncResult
[ComVisibleAttribute(true)]
public interface class IAsyncResult
/** @attribute ComVisibleAttribute(true) */
public interface IAsyncResult
ComVisibleAttribute(true)
public interface IAsyncResult
Note
L'interfaccia IAsyncResult viene implementata da classi contenenti metodi in grado di operare in modo asincrono. Un'operazione asincrona viene iniziata dal tipo restituito dei metodi, ad esempio FileStream.BeginRead, e viene conclusa dal tipo del terzo parametro dei metodi, ad esempio FileStream.EndRead. Gli oggetti IAsyncResult vengono inoltre passati ai metodi richiamati dai delegati AsyncCallback al completamento dell'operazione asincrona.
Un oggetto che supporta l'interfaccia IAsyncResult archivia le informazioni di stato per un'operazione asincrona e fornisce un oggetto di sincronizzazione per consentire la segnalazione ai thread al termine dell'operazione.
Per una descrizione dettagliata delle modalità di utilizzo dell'interfaccia IAsyncResult, vedere l'argomento Chiamata asincrona dei metodi sincroni.
Esempio
Nell'esempio che segue viene illustrato l'utilizzo di IAsyncResult per l'ottenimento del valore restituito di un'operazione asincrona.
' 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
// Asynchronous Callback method.
public static void MyCallback(IAsyncResult ar) {
// Obtains the last parameter of the delegate call.
int value = Convert.ToInt32(ar.AsyncState);
// Obtains return value from the delegate call using EndInvoke.
AsyncResult aResult = (AsyncResult)ar;
SampSyncSqrDelegate temp = (SampSyncSqrDelegate)aResult.AsyncDelegate;
int result = temp.EndInvoke(ar);
Console.Write("Simple.SomeMethod (AsyncCallback): Result of ");
Console.WriteLine("{0} in SampleSynchronized.Square is {1} ", value, result);
}
// Asynchronous Callback method.
static void MyCallback( IAsyncResult^ ar )
{
// Obtains the last parameter of the delegate call.
int value = Convert::ToInt32( ar->AsyncState );
// Obtains return value from the delegate call using EndInvoke.
AsyncResult^ aResult = dynamic_cast<AsyncResult^>(ar);
SampSyncSqrDelegate^ temp = static_cast<SampSyncSqrDelegate^>(aResult->AsyncDelegate);
int result = temp->EndInvoke( ar );
Console::Write( "Simple::SomeMethod (AsyncCallback): Result of " );
Console::WriteLine( " {0} in SampleSynchronized::Square is {1} ", value, result );
}
// 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
Nell'esempio che segue viene illustrata l'attesa del completamento di un'operazione asincrona.
Imports System
Imports System.Threading
Imports System.Runtime.Remoting
Imports System.Runtime.Remoting.Contexts
Imports System.Runtime.Remoting.Messaging
'
' Context-Bound type with Synchronization Context Attribute
'
<Synchronization()> Public Class SampleSyncronized
Inherits ContextBoundObject
' A method that does some work - returns the square of the given number
Public Function Square(i As Integer) As Integer
Console.Write("SampleSyncronized.Square called. ")
Console.WriteLine("The hash of the current thread is: {0}", Thread.CurrentThread.GetHashCode())
Return i * i
End Function 'Square
End Class 'SampleSyncronized
'
' Async delegate used to call a method with this signature asynchronously
'
Delegate Function SampSyncSqrDelegate(i As Integer) As Integer
'Main sample class
Public Class AsyncResultSample
Public Shared Sub Main()
Dim callParameter As Integer = 0
Dim callResult As Integer = 0
'Create an instance of a context-bound type SampleSynchronized
'Because SampleSynchronized is context-bound, the object sampSyncObj
'is a transparent proxy
Dim sampSyncObj As New SampleSyncronized()
'call the method synchronously
Console.Write("Making a synchronous call on the object. ")
Console.WriteLine("The hash of the current thread is: {0}", Thread.CurrentThread.GetHashCode())
callParameter = 10
callResult = sampSyncObj.Square(callParameter)
Console.WriteLine("Result of calling sampSyncObj.Square with {0} is {1}.", callParameter, callResult)
Console.WriteLine("")
Console.WriteLine("")
'call the method asynchronously
Console.Write("Making an asynchronous call on the object. ")
Console.WriteLine("The hash of the current thread is: {0}", Thread.CurrentThread.GetHashCode())
Dim sampleDelegate As New SampSyncSqrDelegate(AddressOf sampSyncObj.Square)
callParameter = 17
Dim aResult As IAsyncResult = sampleDelegate.BeginInvoke(callParameter, Nothing, Nothing)
'Wait for the call to complete
aResult.AsyncWaitHandle.WaitOne()
callResult = sampleDelegate.EndInvoke(aResult)
Console.WriteLine("Result of calling sampSyncObj.Square with {0} is {1}.", callParameter, callResult)
End Sub 'Main
End Class 'AsyncResultSample
using System;
using System.Threading;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Contexts;
using System.Runtime.Remoting.Messaging;
//
// Context-Bound type with Synchronization Context Attribute
//
[Synchronization()]
public class SampleSyncronized : ContextBoundObject
{
// A method that does some work - returns the square of the given number
public int Square(int i)
{
Console.Write("SampleSyncronized.Square called. ");
Console.WriteLine("The hash of the current thread is: {0}", Thread.CurrentThread.GetHashCode());
return i*i;
}
}
//
// Async delegate used to call a method with this signature asynchronously
//
public delegate int SampSyncSqrDelegate(int i);
//Main sample class
public class AsyncResultSample
{
public static void Main()
{
int callParameter = 0;
int callResult = 0;
//Create an instance of a context-bound type SampleSynchronized
//Because SampleSynchronized is context-bound, the object sampSyncObj
//is a transparent proxy
SampleSyncronized sampSyncObj = new SampleSyncronized();
//call the method synchronously
Console.Write("Making a synchronous call on the object. ");
Console.WriteLine("The hash of the current thread is: {0}", Thread.CurrentThread.GetHashCode());
callParameter = 10;
callResult = sampSyncObj.Square(callParameter);
Console.WriteLine("Result of calling sampSyncObj.Square with {0} is {1}.\n\n", callParameter, callResult);
//call the method asynchronously
Console.Write("Making an asynchronous call on the object. ");
Console.WriteLine("The hash of the current thread is: {0}", Thread.CurrentThread.GetHashCode());
SampSyncSqrDelegate sampleDelegate = new SampSyncSqrDelegate(sampSyncObj.Square);
callParameter = 17;
IAsyncResult aResult = sampleDelegate.BeginInvoke(callParameter, null, null);
//Wait for the call to complete
aResult.AsyncWaitHandle.WaitOne();
callResult = sampleDelegate.EndInvoke(aResult);
Console.WriteLine("Result of calling sampSyncObj.Square with {0} is {1}.", callParameter, callResult);
}
}
using namespace System;
using namespace System::Threading;
using namespace System::Runtime::Remoting;
using namespace System::Runtime::Remoting::Contexts;
using namespace System::Runtime::Remoting::Messaging;
//
// Context-Bound type with Synchronization Context Attribute
//
public ref class SampleSyncronized: public ContextBoundObject
{
public:
// A method that does some work - returns the square of the given number
int Square( int i )
{
Console::Write( "SampleSyncronized::Square called. " );
Console::WriteLine( "The hash of the current thread is: {0}", Thread::CurrentThread->GetHashCode() );
return i * i;
}
};
delegate int SampSyncSqrDelegate( //
// Async delegate used to call a method with this signature asynchronously
//
int i );
//Main sample class
int main()
{
int callParameter = 0;
int callResult = 0;
//Create an instance of a context-bound type SampleSynchronized
//Because SampleSynchronized is context-bound, the Object* sampSyncObj
//is a transparent proxy
SampleSyncronized^ sampSyncObj = gcnew SampleSyncronized;
//call the method synchronously
Console::Write( "Making a synchronous call on the Object*. " );
Console::WriteLine( "The hash of the current thread is: {0}", Thread::CurrentThread->GetHashCode() );
callParameter = 10;
callResult = sampSyncObj->Square( callParameter );
Console::WriteLine( "Result of calling sampSyncObj.Square with {0} is {1}.\n\n", callParameter, callResult );
//call the method asynchronously
Console::Write( "Making an asynchronous call on the Object*. " );
Console::WriteLine( "The hash of the current thread is: {0}", Thread::CurrentThread->GetHashCode() );
SampSyncSqrDelegate^ sampleDelegate = gcnew SampSyncSqrDelegate( sampSyncObj, &SampleSyncronized::Square );
callParameter = 17;
IAsyncResult^ aResult = sampleDelegate->BeginInvoke( callParameter, nullptr, 0 );
//Wait for the call to complete
aResult->AsyncWaitHandle->WaitOne();
callResult = sampleDelegate->EndInvoke( aResult );
Console::WriteLine( "Result of calling sampSyncObj.Square with {0} is {1}.", callParameter, callResult );
}
Piattaforme
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile per Pocket PC, Windows Mobile per Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework non supporta tutte le versioni di ciascuna piattaforma. Per un elenco delle versioni supportate, vedere Requisiti di sistema.
Informazioni sulla versione
.NET Framework
Supportato in: 2.0 1.1 1.0
.NET Compact Framework
Supportato in: 2.0 1.0