TaskCompletionSource<TResult> 类

参考

定义

命名空间:: System.Threading.Tasks

程序集:: System.Threading.Tasks.dll

程序集:: System.Runtime.dll

程序集:: mscorlib.dll

程序集:: netstandard.dll

重要

一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。

表示未绑定到委托的 Task<TResult> 的制造者方，并通过 Task 属性提供对使用者方的访问。

generic <typename TResult>
public ref class TaskCompletionSource

public class TaskCompletionSource<TResult>

type TaskCompletionSource<'Result> = class

Public Class TaskCompletionSource(Of TResult)

类型参数

TResult

与此 TaskCompletionSource<TResult>关联的结果值的类型。

继承: Object
TaskCompletionSource<TResult>

示例

以下示例演示如何使用 TaskCompletionSource<TResult>：

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

注解

在许多情况下，启用 Task<TResult> 表示外部异步操作非常有用。 TaskCompletionSource<TResult> 出于此目的提供。它允许创建可分发给使用者的任务。使用者可以使用与处理任务成员变量的任何其他方案相同的任务成员。但是，与大多数任务不同，TaskCompletionSource 创建的任务的状态由 TaskCompletionSource 上的方法显式控制。这使外部异步操作的完成能够传播到基础任务。分离还可确保使用者无法在无法访问相应的 TaskCompletionSource 的情况下转换状态。有关详细信息，请参阅使用 .NET 并行编程的 TaskCompletionSource<TResult> 的条目。

并行扩展示例还包含如何使用TaskCompletionSource<TResult>的示例。

构造函数

TaskCompletionSource<TResult>()	创建一个 TaskCompletionSource<TResult>。
TaskCompletionSource<TResult>(Object)	使用指定的状态创建一个 TaskCompletionSource<TResult>。
TaskCompletionSource<TResult>(Object, TaskCreationOptions)	使用指定的状态和选项创建一个 TaskCompletionSource<TResult>。
TaskCompletionSource<TResult>(TaskCreationOptions)	使用指定的选项创建一个 TaskCompletionSource<TResult>。

属性

Task	获取由此 Task<TResult> 创建的 TaskCompletionSource<TResult>。

方法

Equals(Object)	确定指定对象是否等于当前对象。 (继承自 Object)
GetHashCode()	作为默认哈希函数。 (继承自 Object)
GetType()	获取当前实例的 Type。 (继承自 Object)
MemberwiseClone()	创建当前 Object 的浅表副本。 (继承自 Object)
SetCanceled()	将基础 Task<TResult> 转换为 Canceled 状态。
SetCanceled(CancellationToken)	使用指定的标记将基础 Task<TResult> 转换为 Canceled 状态。
SetException(Exception)	将基础 Task<TResult> 转换为 Faulted 状态，并将其绑定到一个指定异常上。
SetException(IEnumerable<Exception>)	将基础 Task<TResult> 转换为 Faulted 状态，并对其绑定一些异常对象。
SetResult(TResult)	将基础 Task<TResult> 转换为 RanToCompletion 状态。
ToString()	返回表示当前对象的字符串。 (继承自 Object)
TrySetCanceled()	尝试将基础 Task<TResult> 转换为 Canceled 状态。
TrySetCanceled(CancellationToken)	尝试将基础 Task<TResult> 转换为 Canceled 状态并启用要存储在取消的任务中的取消标记。
TrySetException(Exception)	尝试将基础 Task<TResult> 转换为 Faulted 状态，并将其绑定到一个指定异常上。
TrySetException(IEnumerable<Exception>)	尝试将基础 Task<TResult> 转换为 Faulted 状态，并对其绑定一些异常对象。
TrySetResult(TResult)	尝试将基础 Task<TResult> 转换为 RanToCompletion 状态。

适用于

线程安全性

所有成员 TaskCompletionSource<TResult> 都是线程安全的，并且可以同时从多个线程使用。

TaskCompletionSource<TResult> 类

定义

类型参数

示例

注解

构造函数

属性

方法

适用于

线程安全性

另请参阅

其他资源