TaskCompletionSource<TResult> 類別
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。
代表未綁定的生產者側 Task<TResult> 與代理人，透過該 Task 資產提供消費者端的存取。
generic <typename TResult>
public ref class TaskCompletionSourcepublic class TaskCompletionSource<TResult>type TaskCompletionSource<'Result> = classPublic Class TaskCompletionSource(Of TResult)類型參數
- TResult
與此 TaskCompletionSource<TResult>結果值相關的類型。
- 繼承
-
TaskCompletionSource<TResult>
範例
以下範例展示了如何使用TaskCompletionSource<TResult>的方式。
using System;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
class TCSDemo
{
// Demonstrated features:
// TaskCompletionSource ctor()
// TaskCompletionSource.SetResult()
// TaskCompletionSource.SetException()
// Task.Result
// Expected results:
// The attempt to get t1.Result blocks for ~1000ms until tcs1 gets signaled. 15 is printed out.
// The attempt to get t2.Result blocks for ~1000ms until tcs2 gets signaled. An exception is printed out.
static void Main()
{
TaskCompletionSource<int> tcs1 = new TaskCompletionSource<int>();
Task<int> t1 = tcs1.Task;
// Start a background task that will complete tcs1.Task
Task.Factory.StartNew(() =>
{
Thread.Sleep(1000);
tcs1.SetResult(15);
});
// The attempt to get the result of t1 blocks the current thread until the completion source gets signaled.
// It should be a wait of ~1000 ms.
Stopwatch sw = Stopwatch.StartNew();
int result = t1.Result;
sw.Stop();
Console.WriteLine("(ElapsedTime={0}): t1.Result={1} (expected 15) ", sw.ElapsedMilliseconds, result);
// ------------------------------------------------------------------
// Alternatively, an exception can be manually set on a TaskCompletionSource.Task
TaskCompletionSource<int> tcs2 = new TaskCompletionSource<int>();
Task<int> t2 = tcs2.Task;
// Start a background Task that will complete tcs2.Task with an exception
Task.Factory.StartNew(() =>
{
Thread.Sleep(1000);
tcs2.SetException(new InvalidOperationException("SIMULATED EXCEPTION"));
});
// The attempt to get the result of t2 blocks the current thread until the completion source gets signaled with either a result or an exception.
// In either case it should be a wait of ~1000 ms.
sw = Stopwatch.StartNew();
try
{
result = t2.Result;
Console.WriteLine("t2.Result succeeded. THIS WAS NOT EXPECTED.");
}
catch (AggregateException e)
{
Console.Write("(ElapsedTime={0}): ", sw.ElapsedMilliseconds);
Console.WriteLine("The following exceptions have been thrown by t2.Result: (THIS WAS EXPECTED)");
for (int j = 0; j < e.InnerExceptions.Count; j++)
{
Console.WriteLine("\n-------------------------------------------------\n{0}", e.InnerExceptions[j].ToString());
}
}
}
}
Imports System.Diagnostics
Imports System.Threading
Imports System.Threading.Tasks
Module TCSDemo
' Demonstrated features:
' TaskCompletionSource ctor()
' TaskCompletionSource.SetResult()
' TaskCompletionSource.SetException()
' Task.Result
' Expected results:
' The attempt to get t1.Result blocks for ~1000ms until tcs1 gets signaled. 15 is printed out.
' The attempt to get t2.Result blocks for ~1000ms until tcs2 gets signaled. An exception is printed out.
Private Sub Main()
Dim tcs1 As New TaskCompletionSource(Of Integer)()
Dim t1 As Task(Of Integer) = tcs1.Task
' Start a background task that will complete tcs1.Task
Task.Factory.StartNew(Sub()
Thread.Sleep(1000)
tcs1.SetResult(15)
End Sub)
' The attempt to get the result of t1 blocks the current thread until the completion source gets signaled.
' It should be a wait of ~1000 ms.
Dim sw As Stopwatch = Stopwatch.StartNew()
Dim result As Integer = t1.Result
sw.Stop()
Console.WriteLine("(ElapsedTime={0}): t1.Result={1} (expected 15) ", sw.ElapsedMilliseconds, result)
' ------------------------------------------------------------------
' Alternatively, an exception can be manually set on a TaskCompletionSource.Task
Dim tcs2 As New TaskCompletionSource(Of Integer)()
Dim t2 As Task(Of Integer) = tcs2.Task
' Start a background Task that will complete tcs2.Task with an exception
Task.Factory.StartNew(Sub()
Thread.Sleep(1000)
tcs2.SetException(New InvalidOperationException("SIMULATED EXCEPTION"))
End Sub)
' The attempt to get the result of t2 blocks the current thread until the completion source gets signaled with either a result or an exception.
' In either case it should be a wait of ~1000 ms.
sw = Stopwatch.StartNew()
Try
result = t2.Result
Console.WriteLine("t2.Result succeeded. THIS WAS NOT EXPECTED.")
Catch e As AggregateException
Console.Write("(ElapsedTime={0}): ", sw.ElapsedMilliseconds)
Console.WriteLine("The following exceptions have been thrown by t2.Result: (THIS WAS EXPECTED)")
For j As Integer = 0 To e.InnerExceptions.Count - 1
Console.WriteLine(vbLf & "-------------------------------------------------" & vbLf & "{0}", e.InnerExceptions(j).ToString())
Next
End Try
End Sub
End Module
備註
在許多情境下，啟用 a Task<TResult> 來表示外部非同步操作是很有用的。 TaskCompletionSource<TResult> 是為此目的而提供的。 它能創造一項可分配給消費者的任務。 消費者可以像在處理任務成員變數的其他情境中一樣使用任務成員。 然而，與大多數任務不同的是，由 TaskCompletionSource 建立的任務狀態是由 TaskCompletionSource 上的方法明確控制。 這使得外部非同步操作的完成能夠傳達到底層任務。 分離也確保消費者無法在未取得對應 TaskCompletionSource 的情況下轉換狀態。 欲了解更多資訊，請參閱 Parallel Programming with .NET 部落格中的條目 The Nature of TaskCompletionSource<TResult>。
建構函式
屬性
| 名稱 | Description |
|---|---|
| Task |
被 Task<TResult> 這個 TaskCompletionSource<TResult>創造出來。 |
方法
適用於
執行緒安全性
所有成員 TaskCompletionSource<TResult> 皆為執行緒安全，且可同時從多個執行緒使用。
