IAsyncResult.IsCompleted 屬性
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
取得值，這個值表示非同步作業是否完成。
public:
property bool IsCompleted { bool get(); };public bool IsCompleted { get; }member this.IsCompleted : boolPublic ReadOnly Property IsCompleted As Boolean屬性值
如果作業完成，則為 true；否則為 false。
範例
下列範例示範如何使用 IsCompleted 的 IAsyncResult 屬性來探索非同步呼叫完成的時間。 在此情況下，會使用 BeginInvoke 委派的 方法來進行非同步呼叫。 當您從服務使用者介面的執行緒進行非同步呼叫時，您可以使用 IsCompleted 屬性來輪詢完成。 輪詢完成這個動作，可在非同步呼叫於 ThreadPool 執行緒上執行的同時，讓呼叫執行緒能夠繼續執行。
此範例包含兩個類別：包含非同步呼叫之方法的 類別，以及包含進行呼叫之方法的 Main 類別。
如需使用委派以非同步方式呼叫方法的詳細資訊和更多範例，請參閱 以非同步方式呼叫同步方法。
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 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);
}
Imports System.Threading
Imports System.Runtime.InteropServices
Namespace Examples.AdvancedProgramming.AsynchronousOperations
Public Class AsyncDemo
' The method to be executed asynchronously.
Public Function TestMethod(ByVal callDuration As Integer, _
<Out> ByRef threadId As Integer) As String
Console.WriteLine("Test method begins.")
Thread.Sleep(callDuration)
threadId = Thread.CurrentThread.ManagedThreadId()
return String.Format("My call time was {0}.", callDuration.ToString())
End Function
End Class
' The delegate must have the same signature as the method
' it will call asynchronously.
Public Delegate Function AsyncMethodCaller(ByVal callDuration As Integer, _
<Out> ByRef threadId As Integer) As String
End Namespace
#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);
// Poll while simulating work.
while(result->IsCompleted == false)
{
Thread::Sleep(250);
Console::Write(".");
}
// Call EndInvoke to retrieve the results.
String^ returnValue = caller->EndInvoke(threadId, result);
Console::WriteLine("\nThe call executed on thread {0}, with return value \"{1}\".",
threadId, returnValue);
}
/* This example produces output similar to the following:
Test method begins.
.............
The call executed on thread 3, with return value "My call time was 3000.".
*/
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);
// Poll while simulating work.
while(result.IsCompleted == false) {
Thread.Sleep(250);
Console.Write(".");
}
// Call EndInvoke to retrieve the results.
string returnValue = caller.EndInvoke(out threadId, result);
Console.WriteLine("\nThe call executed on thread {0}, with return value \"{1}\".",
threadId, returnValue);
}
}
}
/* This example produces output similar to the following:
Test method begins.
.............
The call executed on thread 3, with return value "My call time was 3000.".
*/
Imports System.Threading
Imports System.Runtime.InteropServices
Namespace Examples.AdvancedProgramming.AsynchronousOperations
Public Class AsyncMain
Shared Sub Main()
' The asynchronous method puts the thread id here.
Dim threadId As Integer
' Create an instance of the test class.
Dim ad As New AsyncDemo()
' Create the delegate.
Dim caller As New AsyncMethodCaller(AddressOf ad.TestMethod)
' Initiate the asynchronous call.
Dim result As IAsyncResult = caller.BeginInvoke(3000, _
threadId, Nothing, Nothing)
' Poll while simulating work.
While result.IsCompleted = False
Thread.Sleep(250)
Console.Write(".")
End While
' Call EndInvoke to retrieve the results.
Dim returnValue As String = caller.EndInvoke(threadId, result)
Console.WriteLine(vbCrLf & _
"The call executed on thread {0}, with return value ""{1}"".", _
threadId, returnValue)
End Sub
End Class
End Namespace
' This example produces output similar to the following:
'
'Test method begins.
'.............
'The call executed on thread 3, with return value "My call time was 3000.".
備註
當此屬性為 true 時，您可以假設您可以放心捨棄任何配置供非同步作業使用的資源。
給實施者的注意事項
實作者通常會傳回私用欄位或內部測試的值做為此屬性的值。
給呼叫者的注意事項
輪詢作業狀態的用戶端 (，而不是等候同步處理物件，) 使用此屬性來判斷作業的狀態。