Task.Run 方法

定義

將指定在 ThreadPool 執行工作排入佇列,並傳回該工作的工作或 Task<TResult> 控制代碼。Queues the specified work to run on the ThreadPool and returns a task or Task<TResult> handle for that work.

多載

Run(Action)

將指定在執行緒集區執行工作排入佇列,並傳回代表該工作的 Task 物件。Queues the specified work to run on the thread pool and returns a Task object that represents that work.

Run(Func<Task>)

將指定在執行緒集區執行的工作排入佇列,並傳回 function 所傳回之工作的 Proxy。Queues the specified work to run on the thread pool and returns a proxy for the task returned by function.

Run(Action, CancellationToken)

將指定在執行緒集區執行工作排入佇列,並傳回代表該工作的 Task 物件。Queues the specified work to run on the thread pool and returns a Task object that represents that work. 取消語彙基元允許取消工作。A cancellation token allows the work to be cancelled.

Run(Func<Task>, CancellationToken)

將指定在執行緒集區執行的工作排入佇列,並傳回 function 所傳回之工作的 Proxy。Queues the specified work to run on the thread pool and returns a proxy for the task returned by function.

Run<TResult>(Func<TResult>, CancellationToken)

將指定在執行緒集區執行工作排入佇列,並傳回代表該工作的 Task(TResult) 物件。Queues the specified work to run on the thread pool and returns a Task(TResult) object that represents that work. 取消語彙基元允許取消工作。A cancellation token allows the work to be cancelled.

Run<TResult>(Func<Task<TResult>>, CancellationToken)

將指定在執行緒集區執行的工作排入佇列,並傳回 function 所傳回之 Task(TResult) 的 Proxy。Queues the specified work to run on the thread pool and returns a proxy for the Task(TResult) returned by function.

Run<TResult>(Func<Task<TResult>>)

將指定在執行緒集區執行的工作排入佇列,並傳回 function 所傳回之 Task(TResult) 的 Proxy。Queues the specified work to run on the thread pool and returns a proxy for the Task(TResult) returned by function.

Run<TResult>(Func<TResult>)

將指定在執行緒集區執行工作排入佇列,並傳回代表該工作的 Task<TResult> 物件。Queues the specified work to run on the thread pool and returns a Task<TResult> object that represents that work.

備註

Run 方法會提供一組多載,可讓您輕鬆地使用預設值來啟動工作。The Run method provides a set of overloads that make it easy to start a task by using default values. 這是 StartNew 多載的輕量替代方式。It is a lightweight alternative to the StartNew overloads.

Run(Action)

將指定在執行緒集區執行工作排入佇列,並傳回代表該工作的 Task 物件。Queues the specified work to run on the thread pool and returns a Task object that represents that work.

public:
 static System::Threading::Tasks::Task ^ Run(Action ^ action);
public static System.Threading.Tasks.Task Run (Action action);
static member Run : Action -> System.Threading.Tasks.Task

參數

action
Action

要以非同步方式執行的工作The work to execute asynchronously

傳回

表示已進入佇列要在 ThreadPool 中執行之工作 (work) 的工作 (task)。A task that represents the work queued to execute in the ThreadPool.

例外狀況

action 參數為 nullThe action parameter was null.

範例

下列範例會定義 ShowThreadInfo 方法,以顯示目前線程的 Thread.ManagedThreadIdThe following example defines a ShowThreadInfo method that displays the Thread.ManagedThreadId of the current thread. 它會直接從應用程式執行緒呼叫,並從傳遞給 Run(Action) 方法的 Action 委派呼叫。It is called directly from the application thread, and is called from the Action delegate passed to the Run(Action) method.

using System;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      ShowThreadInfo("Application");

      var t = Task.Run(() => ShowThreadInfo("Task") );
      t.Wait();
   }

   static void ShowThreadInfo(String s)
   {
      Console.WriteLine("{0} Thread ID: {1}",
                        s, Thread.CurrentThread.ManagedThreadId);
   }
}
// The example displays the following output:
//       Application thread ID: 1
//       Task thread ID: 3
Imports System.Threading
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      ShowThreadInfo("Application")

      Dim t As Task = Task.Run(Sub() ShowThreadInfo("Task") )
      t.Wait()
   End Sub
   
   Private Sub ShowThreadInfo(s As String)
      Console.WriteLine("{0} Thread ID: {1}",
                        s, Thread.CurrentThread.ManagedThreadId)
   End Sub
End Module
' The example displays output like the following:
'    Application thread ID: 1
'    Task thread ID: 3

下列範例類似于上一個範例,不同之處在于它會使用 lambda 運算式來定義工作要執行的程式碼。The following example is similar to the previous one, except that it uses a lambda expression to define the code that the task is to execute.

using System;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      Console.WriteLine("Application thread ID: {0}",
                        Thread.CurrentThread.ManagedThreadId);
      var t = Task.Run(() => {  Console.WriteLine("Task thread ID: {0}",
                                   Thread.CurrentThread.ManagedThreadId);
                             } );
      t.Wait();
   }
}
// The example displays the following output:
//       Application thread ID: 1
//       Task thread ID: 3
Imports System.Threading
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Console.WriteLine("Application thread ID: {0}",
                        Thread.CurrentThread.ManagedThreadId)
      Dim t As Task = Task.Run(Sub()
                                  Console.WriteLine("Task thread ID: {0}",
                                                    Thread.CurrentThread.ManagedThreadId)
                               End Sub)
      t.Wait()
   End Sub
End Module
' The example displays output like the following:
'    Application thread ID: 1
'    Task thread ID: 3

範例顯示非同步工作會在與主應用程式執行緒不同的執行緒上執行。The examples show that the asynchronous task executes on a different thread than the main application thread.

呼叫 Wait 方法可確保工作完成,並在應用程式結束之前顯示其輸出。The call to the Wait method ensures that the task completes and displays its output before the application ends. 否則,Main 方法可能會在工作完成之前完成。Otherwise, it is possible that the Main method will complete before the task finishes.

下列範例說明 Run(Action) 方法。The following example illustrates the Run(Action) method. 它會定義目錄名稱的陣列,並啟動個別工作來抓取每個目錄中的檔案名。It defines an array of directory names and starts a separate task to retrieve the file names in each directory. 所有工作都會將檔案名寫入單一 ConcurrentBag<T> 物件。All tasks write the file names to a single ConcurrentBag<T> object. 然後,此範例會呼叫 WaitAll(Task[]) 方法,以確保所有工作都已完成,然後顯示寫入 ConcurrentBag<T> 物件之檔案名總數的計數。The example then calls the WaitAll(Task[]) method to ensure that all tasks have completed, and then displays a count of the total number of file names written to the ConcurrentBag<T> object.

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      var list = new ConcurrentBag<string>();
      string[] dirNames = { ".", ".." };
      List<Task> tasks = new List<Task>();
      foreach (var dirName in dirNames) {
         Task t = Task.Run( () => { foreach(var path in Directory.GetFiles(dirName)) 
                                       list.Add(path); }  );
         tasks.Add(t);
      }
      Task.WaitAll(tasks.ToArray());
      foreach (Task t in tasks)
         Console.WriteLine("Task {0} Status: {1}", t.Id, t.Status);
         
      Console.WriteLine("Number of files read: {0}", list.Count);
   }
}
// The example displays output like the following:
//       Task 1 Status: RanToCompletion
//       Task 2 Status: RanToCompletion
//       Number of files read: 23
Imports System.Collections.Concurrent
Imports System.Collections.Generic
Imports System.IO
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Dim list As New ConcurrentBag(Of String)()
      Dim dirNames() As String = { ".", ".." }
      Dim tasks As New List(Of Task)()
      For Each dirName In dirNames 
         Dim t As Task = Task.Run( Sub()
                                      For Each path In Directory.GetFiles(dirName) 
                                         list.Add(path)
                                      Next
                                   End Sub  )
         tasks.Add(t)
      Next
      Task.WaitAll(tasks.ToArray())
      For Each t In tasks
         Console.WriteLine("Task {0} Status: {1}", t.Id, t.Status)
      Next   
      Console.WriteLine("Number of files read: {0}", list.Count)
   End Sub
End Module
' The example displays output like the following:
'       Task 1 Status: RanToCompletion
'       Task 2 Status: RanToCompletion
'       Number of files read: 23

備註

Run 方法可讓您在單一方法呼叫中建立和執行工作,而且是 StartNew 方法的較簡單替代方式。The Run method allows you to create and execute a task in a single method call and is a simpler alternative to the StartNew method. 它會使用下列預設值來建立工作:It creates a task with the following default values:

如需處理工作作業所擲回之例外狀況的詳細資訊,請參閱例外狀況處理For information on handling exceptions thrown by task operations, see Exception Handling.

另請參閱

Run(Func<Task>)

將指定在執行緒集區執行的工作排入佇列,並傳回 function 所傳回之工作的 Proxy。Queues the specified work to run on the thread pool and returns a proxy for the task returned by function.

public:
 static System::Threading::Tasks::Task ^ Run(Func<System::Threading::Tasks::Task ^> ^ function);
public static System.Threading.Tasks.Task Run (Func<System.Threading.Tasks.Task> function);
static member Run : Func<System.Threading.Tasks.Task> -> System.Threading.Tasks.Task
Public Shared Function Run (function As Func(Of Task)) As Task

參數

function
Func<Task>

要以非同步方式執行的工作The work to execute asynchronously

傳回

表示 function 所傳回工作之 Proxy 的工作。A task that represents a proxy for the task returned by function.

例外狀況

function 參數為 nullThe function parameter was null.

備註

如需處理工作作業所擲回之例外狀況的詳細資訊,請參閱例外狀況處理For information on handling exceptions thrown by task operations, see Exception Handling.

另請參閱

Run(Action, CancellationToken)

將指定在執行緒集區執行工作排入佇列,並傳回代表該工作的 Task 物件。Queues the specified work to run on the thread pool and returns a Task object that represents that work. 取消語彙基元允許取消工作。A cancellation token allows the work to be cancelled.

public:
 static System::Threading::Tasks::Task ^ Run(Action ^ action, System::Threading::CancellationToken cancellationToken);
public static System.Threading.Tasks.Task Run (Action action, System.Threading.CancellationToken cancellationToken);
static member Run : Action * System.Threading.CancellationToken -> System.Threading.Tasks.Task

參數

action
Action

要以非同步方式執行的工作The work to execute asynchronously

cancellationToken
CancellationToken

可以用來取消工作的取消語彙基元A cancellation token that can be used to cancel the work

傳回

代表已進入佇列,並要在執行緒集區中執行之工作 (work) 的工作 (task)。A task that represents the work queued to execute in the thread pool.

例外狀況

action 參數為 nullThe action parameter was null.

已取消這項工作。The task has been canceled.

cancellationToken 相關聯的 CancellationTokenSource 已經處置。The CancellationTokenSource associated with cancellationToken was disposed.

範例

下列範例會呼叫 Run(Action, CancellationToken) 方法,以建立可逐一查看 C:\Windows\System32 目錄中檔案的工作。The following example calls the Run(Action, CancellationToken) method to create a task that iterates the files in the C:\Windows\System32 directory. Lambda 運算式會呼叫 Parallel.ForEach 方法,將每個檔案的相關資訊新增至 List<T> 物件。The lambda expression calls the Parallel.ForEach method to add information about each file to a List<T> object. Parallel.ForEach 迴圈所叫用的每個已卸離的嵌套工作都會檢查解除標記的狀態,而且如果要求取消,則會呼叫 CancellationToken.ThrowIfCancellationRequested 方法。Each detached nested task invoked by the Parallel.ForEach loop checks the state of the cancellation token and, if cancellation is requested, calls the CancellationToken.ThrowIfCancellationRequested method. 當呼叫執行緒呼叫 Task.Wait 方法時,CancellationToken.ThrowIfCancellationRequested 方法會擲回 catch 區塊中處理的 OperationCanceledException 例外狀況。The CancellationToken.ThrowIfCancellationRequested method throws an OperationCanceledException exception that is handled in a catch block when the calling thread calls the Task.Wait method.

using System;
using System.Collections.Generic;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   public static async Task Main()
   {
      var tokenSource = new CancellationTokenSource();
      var token = tokenSource.Token;
      var files = new List<Tuple<string, string, long, DateTime>>();

      var t = Task.Run( () => { string dir = "C:\\Windows\\System32\\";
                                object obj = new Object();
                                if (Directory.Exists(dir)) {
                                   Parallel.ForEach(Directory.GetFiles(dir),
                                   f => {
                                           if (token.IsCancellationRequested)
                                              token.ThrowIfCancellationRequested();
                                           var fi = new FileInfo(f);
                                           lock(obj) {
                                              files.Add(Tuple.Create(fi.Name, fi.DirectoryName, fi.Length, fi.LastWriteTimeUtc));          
                                           }
                                      });
                                 }
                              }
                        , token);
      await Task.Yield();
      tokenSource.Cancel();
      try {
         await t;
         Console.WriteLine("Retrieved information for {0} files.", files.Count);
      }
      catch (AggregateException e) {
         Console.WriteLine("Exception messages:");
         foreach (var ie in e.InnerExceptions)
            Console.WriteLine("   {0}: {1}", ie.GetType().Name, ie.Message);

         Console.WriteLine("\nTask status: {0}", t.Status);       
      }
      finally {
         tokenSource.Dispose();
      }
   }
}
// The example displays the following output:
//       Exception messages:
//          TaskCanceledException: A task was canceled.
//          TaskCanceledException: A task was canceled.
//          ...
//       
//       Task status: Canceled
Imports System.Collections.Generic
Imports System.IO
Imports System.Threading
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Dim tokenSource As New CancellationTokenSource()
      Dim token As CancellationToken = tokenSource.Token
      Dim files As New List(Of Tuple(Of String, String, Long, Date))()

      Dim t As Task = Task.Run( Sub()
                                   Dim dir As String = "C:\Windows\System32\"
                                   Dim obj As New Object()
                                   If Directory.Exists(dir)Then
                                      Parallel.ForEach(Directory.GetFiles(dir), 
                                         Sub(f)
                                            If token.IsCancellationRequested Then
                                               token.ThrowIfCancellationRequested()
                                            End If  
                                            Dim fi As New FileInfo(f)
                                            SyncLock(obj)
                                              files.Add(Tuple.Create(fi.Name, fi.DirectoryName, fi.Length, fi.LastWriteTimeUtc))          
                                            End SyncLock
                                         End Sub)
                                   End If
                                End Sub, token)
      tokenSource.Cancel()
      Try
         t.Wait() 
         Console.WriteLine("Retrieved information for {0} files.", files.Count)
      Catch e As AggregateException
         Console.WriteLine("Exception messages:")
         For Each ie As Exception In e.InnerExceptions
            Console.WriteLine("   {0}:{1}", ie.GetType().Name, ie.Message)
         Next
         Console.WriteLine()
         Console.WriteLine("Task status: {0}", t.Status)       
      Finally
         tokenSource.Dispose()
      End Try
   End Sub
End Module
' The example displays the following output:
'       Exception messages:
'          TaskCanceledException: A task was canceled.
'       
'       Task status: Canceled

備註

如果在工作開始執行之前要求取消,則工作不會執行。If cancellation is requested before the task begins execution, the task does not execute. 相反地,它會設定為 Canceled 狀態,並擲回 TaskCanceledException 例外狀況。Instead it is set to the Canceled state and throws a TaskCanceledException exception.

Run(Action, CancellationToken) 方法是 TaskFactory.StartNew(Action, CancellationToken) 方法較簡單的替代方式。The Run(Action, CancellationToken) method is a simpler alternative to the TaskFactory.StartNew(Action, CancellationToken) method. 它會使用下列預設值來建立工作:It creates a task with the following default values:

如需處理工作作業所擲回之例外狀況的詳細資訊,請參閱例外狀況處理For information on handling exceptions thrown by task operations, see Exception Handling.

另請參閱

Run(Func<Task>, CancellationToken)

將指定在執行緒集區執行的工作排入佇列,並傳回 function 所傳回之工作的 Proxy。Queues the specified work to run on the thread pool and returns a proxy for the task returned by function.

public:
 static System::Threading::Tasks::Task ^ Run(Func<System::Threading::Tasks::Task ^> ^ function, System::Threading::CancellationToken cancellationToken);
public static System.Threading.Tasks.Task Run (Func<System.Threading.Tasks.Task> function, System.Threading.CancellationToken cancellationToken);
static member Run : Func<System.Threading.Tasks.Task> * System.Threading.CancellationToken -> System.Threading.Tasks.Task

參數

function
Func<Task>

要以非同步方式執行的工作。The work to execute asynchronously.

cancellationToken
CancellationToken

應該用來取消工作的取消語彙基元。A cancellation token that should be used to cancel the work.

傳回

表示 function 所傳回工作之 Proxy 的工作。A task that represents a proxy for the task returned by function.

例外狀況

function 參數為 nullThe function parameter was null.

已取消這項工作。The task has been canceled.

cancellationToken 相關聯的 CancellationTokenSource 已經處置。The CancellationTokenSource associated with cancellationToken was disposed.

備註

如需處理工作作業所擲回之例外狀況的詳細資訊,請參閱例外狀況處理For information on handling exceptions thrown by task operations, see Exception Handling.

另請參閱

Run<TResult>(Func<TResult>, CancellationToken)

將指定在執行緒集區執行工作排入佇列,並傳回代表該工作的 Task(TResult) 物件。Queues the specified work to run on the thread pool and returns a Task(TResult) object that represents that work. 取消語彙基元允許取消工作。A cancellation token allows the work to be cancelled.

public:
generic <typename TResult>
 static System::Threading::Tasks::Task<TResult> ^ Run(Func<TResult> ^ function, System::Threading::CancellationToken cancellationToken);
public static System.Threading.Tasks.Task<TResult> Run<TResult> (Func<TResult> function, System.Threading.CancellationToken cancellationToken);
static member Run : Func<'Result> * System.Threading.CancellationToken -> System.Threading.Tasks.Task<'Result>

類型參數

TResult

工作的結果類型。The result type of the task.

參數

function
Func<TResult>

要以非同步方式執行的工作The work to execute asynchronously

cancellationToken
CancellationToken

應該用來取消工作的取消語彙基元A cancellation token that should be used to cancel the work

傳回

Task(TResult),代表已排入佇列要在執行緒集區中執行的工作。A Task(TResult) that represents the work queued to execute in the thread pool.

例外狀況

function 參數為 nullThe function parameter is null.

已取消這項工作。The task has been canceled.

cancellationToken 相關聯的 CancellationTokenSource 已經處置。The CancellationTokenSource associated with cancellationToken was disposed.

範例

下列範例會建立20個會迴圈的工作,直到計數器遞增為2000000的值為止。The following example creates 20 tasks that will loop until a counter is incremented to a value of 2 million. 當前10個工作達到2000000時,解除標記會取消,而且會取消任何計數器尚未達到2000000的工作。When the first 10 tasks reach 2 million, the cancellation token is cancelled, and any tasks whose counters have not reached 2 million are cancelled. 此範例會顯示可能的輸出。The example shows possible output.

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      var tasks = new List<Task<int>>();
      var source = new CancellationTokenSource();
      var token = source.Token;
      int completedIterations = 0;

      for (int n = 0; n <= 19; n++)
         tasks.Add(Task.Run( () => { int iterations = 0;
                                     for (int ctr = 1; ctr <= 2000000; ctr++) {
                                         token.ThrowIfCancellationRequested();
                                         iterations++;
                                     }
                                     Interlocked.Increment(ref completedIterations);
                                     if (completedIterations >= 10)
                                        source.Cancel();
                                     return iterations; }, token));

      Console.WriteLine("Waiting for the first 10 tasks to complete...\n");
      try  {
         Task.WaitAll(tasks.ToArray());
      }
      catch (AggregateException) {
         Console.WriteLine("Status of tasks:\n");
         Console.WriteLine("{0,10} {1,20} {2,14:N0}", "Task Id",
                           "Status", "Iterations");
         foreach (var t in tasks)
            Console.WriteLine("{0,10} {1,20} {2,14}",
                              t.Id, t.Status,
                              t.Status != TaskStatus.Canceled ? t.Result.ToString("N0") : "n/a");
      }
   }
}
// The example displays output like the following:
//    Waiting for the first 10 tasks to complete...
//    Status of tasks:
//
//       Task Id               Status     Iterations
//             1      RanToCompletion      2,000,000
//             2      RanToCompletion      2,000,000
//             3      RanToCompletion      2,000,000
//             4      RanToCompletion      2,000,000
//             5      RanToCompletion      2,000,000
//             6      RanToCompletion      2,000,000
//             7      RanToCompletion      2,000,000
//             8      RanToCompletion      2,000,000
//             9      RanToCompletion      2,000,000
//            10             Canceled            n/a
//            11             Canceled            n/a
//            12             Canceled            n/a
//            13             Canceled            n/a
//            14             Canceled            n/a
//            15             Canceled            n/a
//            16      RanToCompletion      2,000,000
//            17             Canceled            n/a
//            18             Canceled            n/a
//            19             Canceled            n/a
//            20             Canceled            n/a
Imports System.Collections.Generic
Imports System.Threading
Imports System.Threading.Tasks

Module Example

   Public Sub Main()
      Dim tasks As New List(Of Task(Of Integer))()
      Dim source As New CancellationTokenSource
      Dim token As CancellationToken = source.Token
      Dim completedIterations As Integer = 0
      
      For n As Integer = 0 To 19
         tasks.Add(Task.Run( Function()
                                Dim iterations As Integer= 0
                                For ctr As Long = 1 To 2000000
                                   token.ThrowIfCancellationRequested()
                                   iterations += 1
                                Next
                                Interlocked.Increment(completedIterations)
                                If completedIterations >= 10 Then source.Cancel()
                                Return iterations
                             End Function, token))
      Next

      Console.WriteLine("Waiting for the first 10 tasks to complete... ")
      Try
         Task.WaitAll(tasks.ToArray())
      Catch e As AggregateException
         Console.WriteLine("Status of tasks:")
         Console.WriteLine()
         Console.WriteLine("{0,10} {1,20} {2,14}", "Task Id",
                           "Status", "Iterations")
         For Each t In tasks
            Console.WriteLine("{0,10} {1,20} {2,14}",
                              t.Id, t.Status,
                              If(t.Status <> TaskStatus.Canceled,
                                 t.Result.ToString("N0"), "n/a"))
         Next
      End Try
   End Sub
End Module
' The example displays output like the following:
'    Waiting for the first 10 tasks to complete...
'    Status of tasks:
'
'       Task Id               Status     Iterations
'             1      RanToCompletion      2,000,000
'             2      RanToCompletion      2,000,000
'             3      RanToCompletion      2,000,000
'             4      RanToCompletion      2,000,000
'             5      RanToCompletion      2,000,000
'             6      RanToCompletion      2,000,000
'             7      RanToCompletion      2,000,000
'             8      RanToCompletion      2,000,000
'             9      RanToCompletion      2,000,000
'            10             Canceled            n/a
'            11             Canceled            n/a
'            12             Canceled            n/a
'            13             Canceled            n/a
'            14             Canceled            n/a
'            15             Canceled            n/a
'            16      RanToCompletion      2,000,000
'            17             Canceled            n/a
'            18             Canceled            n/a
'            19             Canceled            n/a
'            20             Canceled            n/a

此範例會逐一查看所有工作,以判斷哪些工作已順利完成且已取消,而不是使用 InnerExceptions 屬性來檢查例外狀況。Instead of using the InnerExceptions property to examine exceptions, the example iterates all tasks to determine which have completed successfully and which have been cancelled. 對於已完成的工作,它會顯示工作所傳回的值。For those that have completed, it displays the value returned by the task.

因為取消是合作的,每個工作都可以決定如何回應取消。Because cancellation is cooperative, each task can decide how to respond to cancellation. 下列範例與第一個類似,不同之處在于解除標記之後,工作會傳回已完成的反覆運算次數,而不是擲回例外狀況。The following example is like the first, except that, once the token is cancelled, tasks return the number of iterations they've completed rather than throw an exception.

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      var tasks = new List<Task<int>>();
      var source = new CancellationTokenSource();
      var token = source.Token;
      int completedIterations = 0;

      for (int n = 0; n <= 19; n++)
         tasks.Add(Task.Run( () => { int iterations = 0;
                                     for (int ctr = 1; ctr <= 2000000; ctr++) {
                                         if (token.IsCancellationRequested)
                                            return iterations;
                                         iterations++;
                                     }
                                     Interlocked.Increment(ref completedIterations);
                                     if (completedIterations >= 10)
                                        source.Cancel();
                                     return iterations; }, token));

      Console.WriteLine("Waiting for the first 10 tasks to complete...\n");
      try  {
         Task.WaitAll(tasks.ToArray());
      }
      catch (AggregateException) {
         Console.WriteLine("Status of tasks:\n");
         Console.WriteLine("{0,10} {1,20} {2,14:N0}", "Task Id",
                           "Status", "Iterations");
         foreach (var t in tasks)
            Console.WriteLine("{0,10} {1,20} {2,14}",
                              t.Id, t.Status,
                              t.Status != TaskStatus.Canceled ? t.Result.ToString("N0") : "n/a");
      }
   }
}
// The example displays output like the following:
//    Status of tasks:
//
//       Task Id               Status     Iterations
//             1      RanToCompletion      2,000,000
//             2      RanToCompletion      2,000,000
//             3      RanToCompletion      2,000,000
//             4      RanToCompletion      2,000,000
//             5      RanToCompletion      2,000,000
//             6      RanToCompletion      2,000,000
//             7      RanToCompletion      2,000,000
//             8      RanToCompletion      2,000,000
//             9      RanToCompletion      2,000,000
//            10      RanToCompletion      1,658,326
//            11      RanToCompletion      1,988,506
//            12      RanToCompletion      2,000,000
//            13      RanToCompletion      1,942,246
//            14      RanToCompletion        950,108
//            15      RanToCompletion      1,837,832
//            16      RanToCompletion      1,687,182
//            17      RanToCompletion        194,548
//            18             Canceled    Not Started
//            19             Canceled    Not Started
//            20             Canceled    Not Started
Imports System.Collections.Generic
Imports System.Threading
Imports System.Threading.Tasks

Module Example

   Public Sub Main()
      Dim tasks As New List(Of Task(Of Integer))()
      Dim source As New CancellationTokenSource
      Dim token As CancellationToken = source.Token
      Dim completedIterations As Integer = 0
      
      For n As Integer = 0 To 19
         tasks.Add(Task.Run( Function()
                                Dim iterations As Integer= 0
                                For ctr As Long = 1 To 2000000
                                   If token.IsCancellationRequested Then
                                      Return iterations
                                   End If
                                   iterations += 1
                                Next
                                Interlocked.Increment(completedIterations)
                                If completedIterations >= 10 Then source.Cancel()
                                Return iterations
                             End Function, token))
      Next

      Try
         Task.WaitAll(tasks.ToArray())
      Catch e As AggregateException
         Console.WriteLine("Status of tasks:")
         Console.WriteLine()
         Console.WriteLine("{0,10} {1,20} {2,14:N0}", "Task Id",
                           "Status", "Iterations")
         For Each t In tasks
            Console.WriteLine("{0,10} {1,20} {2,14}",
                              t.Id, t.Status,
                              If(t.Status <> TaskStatus.Canceled,
                                 t.Result.ToString("N0"), "Not Started"))
         Next
      End Try
   End Sub
End Module
' The example displays output like the following:
'    Status of tasks:
'
'       Task Id               Status     Iterations
'             1      RanToCompletion      2,000,000
'             2      RanToCompletion      2,000,000
'             3      RanToCompletion      2,000,000
'             4      RanToCompletion      2,000,000
'             5      RanToCompletion      2,000,000
'             6      RanToCompletion      2,000,000
'             7      RanToCompletion      2,000,000
'             8      RanToCompletion      2,000,000
'             9      RanToCompletion      2,000,000
'            10      RanToCompletion      1,658,326
'            11      RanToCompletion      1,988,506
'            12      RanToCompletion      2,000,000
'            13      RanToCompletion      1,942,246
'            14      RanToCompletion        950,108
'            15      RanToCompletion      1,837,832
'            16      RanToCompletion      1,687,182
'            17      RanToCompletion        194,548
'            18             Canceled    Not Started
'            19             Canceled    Not Started
'            20             Canceled    Not Started

此範例仍然必須處理 AggregateException 的例外狀況,因為在要求取消時未啟動的任何工作仍然會擲回例外狀況。The example still must handle the AggregateException exception, since any tasks that have not started when cancellation is requested still throw an exception.

備註

如果在工作開始執行之前要求取消,則工作不會執行。If cancellation is requested before the task begins execution, the task does not execute. 相反地,它會設定為 Canceled 狀態,並擲回 TaskCanceledException 例外狀況。Instead it is set to the Canceled state and throws a TaskCanceledException exception.

Run 方法是 StartNew 方法較簡單的替代方式。The Run method is a simpler alternative to the StartNew method. 它會使用下列預設值來建立工作:It creates a task with the following default values:

如需處理工作作業所擲回之例外狀況的詳細資訊,請參閱例外狀況處理For information on handling exceptions thrown by task operations, see Exception Handling.

另請參閱

Run<TResult>(Func<Task<TResult>>, CancellationToken)

將指定在執行緒集區執行的工作排入佇列,並傳回 function 所傳回之 Task(TResult) 的 Proxy。Queues the specified work to run on the thread pool and returns a proxy for the Task(TResult) returned by function.

public:
generic <typename TResult>
 static System::Threading::Tasks::Task<TResult> ^ Run(Func<System::Threading::Tasks::Task<TResult> ^> ^ function, System::Threading::CancellationToken cancellationToken);
public static System.Threading.Tasks.Task<TResult> Run<TResult> (Func<System.Threading.Tasks.Task<TResult>> function, System.Threading.CancellationToken cancellationToken);
static member Run : Func<System.Threading.Tasks.Task<'Result>> * System.Threading.CancellationToken -> System.Threading.Tasks.Task<'Result>

類型參數

TResult

Proxy 工作傳回的結果類型。The type of the result returned by the proxy task.

參數

function
Func<Task<TResult>>

要以非同步方式執行的工作The work to execute asynchronously

cancellationToken
CancellationToken

應該用來取消工作的取消語彙基元A cancellation token that should be used to cancel the work

傳回

Task(TResult),代表 Task(TResult) 所傳回之 function 的 Proxy。A Task(TResult) that represents a proxy for the Task(TResult) returned by function.

例外狀況

function 參數為 nullThe function parameter was null.

已取消這項工作。The task has been canceled.

cancellationToken 相關聯的 CancellationTokenSource 已經處置。The CancellationTokenSource associated with cancellationToken was disposed.

備註

如需處理工作作業所擲回之例外狀況的詳細資訊,請參閱例外狀況處理For information on handling exceptions thrown by task operations, see Exception Handling.

另請參閱

Run<TResult>(Func<Task<TResult>>)

將指定在執行緒集區執行的工作排入佇列,並傳回 function 所傳回之 Task(TResult) 的 Proxy。Queues the specified work to run on the thread pool and returns a proxy for the Task(TResult) returned by function.

public:
generic <typename TResult>
 static System::Threading::Tasks::Task<TResult> ^ Run(Func<System::Threading::Tasks::Task<TResult> ^> ^ function);
public static System.Threading.Tasks.Task<TResult> Run<TResult> (Func<System.Threading.Tasks.Task<TResult>> function);
static member Run : Func<System.Threading.Tasks.Task<'Result>> -> System.Threading.Tasks.Task<'Result>
Public Shared Function Run(Of TResult) (function As Func(Of Task(Of TResult))) As Task(Of TResult)

類型參數

TResult

Proxy 工作傳回的結果類型。The type of the result returned by the proxy task.

參數

function
Func<Task<TResult>>

要以非同步方式執行的工作The work to execute asynchronously

傳回

Task(TResult),代表 Task(TResult) 所傳回之 function 的 Proxy。A Task(TResult) that represents a proxy for the Task(TResult) returned by function.

例外狀況

function 參數為 nullThe function parameter was null.

備註

如需處理工作作業所擲回之例外狀況的詳細資訊,請參閱例外狀況處理For information on handling exceptions thrown by task operations, see Exception Handling.

另請參閱

Run<TResult>(Func<TResult>)

將指定在執行緒集區執行工作排入佇列,並傳回代表該工作的 Task<TResult> 物件。Queues the specified work to run on the thread pool and returns a Task<TResult> object that represents that work.

public:
generic <typename TResult>
 static System::Threading::Tasks::Task<TResult> ^ Run(Func<TResult> ^ function);
public static System.Threading.Tasks.Task<TResult> Run<TResult> (Func<TResult> function);
static member Run : Func<'Result> -> System.Threading.Tasks.Task<'Result>
Public Shared Function Run(Of TResult) (function As Func(Of TResult)) As Task(Of TResult)

類型參數

TResult

工作的傳回類型。The return type of the task.

參數

function
Func<TResult>

要以非同步方式執行的工作。The work to execute asynchronously.

傳回

代表已排入佇列要在執行緒集區中執行之工作 (work) 的工作 (task) 物件。A task object that represents the work queued to execute in the thread pool.

例外狀況

function 參數為 nullThe function parameter is null.

範例

下列範例會計算代表已發行書籍之文字檔中的大約單字數。The following example counts the approximate number of words in text files that represent published books. 每項工作都負責開啟檔案、以非同步方式讀取其完整內容,以及使用正則運算式來計算字數。Each task is responsible for opening a file, reading its entire contents asynchronously, and calculating the word count by using a regular expression. 呼叫 WaitAll(Task[]) 方法,以確保所有工作都已完成,然後才會在主控台中顯示每一本書的字數統計。The WaitAll(Task[]) method is called to ensure that all tasks have completed before displaying the word count of each book to the console.

using System;
using System.IO;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      string pattern = @"\p{P}*\s+";
      string[] titles = { "Sister Carrie", "The Financier" };
      Task<int>[] tasks = new Task<int>[titles.Length];

      for (int ctr = 0; ctr < titles.Length; ctr++) {
         string s = titles[ctr];
         tasks[ctr] = Task.Run( () => {
                                   // Number of words.
                                   int nWords = 0;
                                   // Create filename from title.
                                   string fn = s + ".txt";
                                   if (File.Exists(fn)) {
                                      StreamReader sr = new StreamReader(fn);
                                      string input = sr.ReadToEndAsync().Result;
                                      nWords = Regex.Matches(input, pattern).Count;
                                   }
                                   return nWords;
                                } );
      }
      Task.WaitAll(tasks);

      Console.WriteLine("Word Counts:\n");
      for (int ctr = 0; ctr < titles.Length; ctr++)
         Console.WriteLine("{0}: {1,10:N0} words", titles[ctr], tasks[ctr].Result);
   }
}
// The example displays the following output:
//       Sister Carrie:    159,374 words
//       The Financier:    196,362 words
Imports System.IO
Imports System.Text.RegularExpressions
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Dim pattern As String = "\p{P}*\s+"
      Dim titles() As String = { "Sister Carrie",
                                 "The Financier" }
      Dim tasks(titles.Length - 1) As Task(Of Integer)

      For ctr As Integer = 0 To titles.Length - 1
         Dim s As String = titles(ctr)
         tasks(ctr) = Task.Run( Function()
                                   ' Number of words.
                                   Dim nWords As Integer = 0
                                   ' Create filename from title.
                                   Dim fn As String = s + ".txt"
                                   If File.Exists(fn) Then
                                      Dim sr As New StreamReader(fn)
                                      Dim input As String = sr.ReadToEndAsync().Result
                                      nWords = Regex.Matches(input, pattern).Count
                                   End If
                                   Return nWords
                                End Function)
      Next
      Task.WaitAll(tasks)

      Console.WriteLine("Word Counts:")
      Console.WriteLine()
      For ctr As Integer = 0 To titles.Length - 1
         Console.WriteLine("{0}: {1,10:N0} words", titles(ctr), tasks(ctr).Result)
      Next
   End Sub
End Module
' The example displays the following output:
'       Sister Carrie:    159,374 words
'       The Financier:    196,362 words

正則運算式 \p{P}*\s+ 符合零個、一個或多個標點符號字元,後面接著一或多個空白字元。The regular expression \p{P}*\s+ matches zero, one, or more punctuation characters followed by one or more white-space characters. 它假設符合的總數目等於大約的字數。It assumes that the total number of matches equals the approximate word count.

備註

Run 方法是 TaskFactory.StartNew(Action) 方法較簡單的替代方式。The Run method is a simpler alternative to the TaskFactory.StartNew(Action) method. 它會使用下列預設值來建立工作:It creates a task with the following default values:

如需處理工作作業所擲回之例外狀況的詳細資訊,請參閱例外狀況處理For information on handling exceptions thrown by task operations, see Exception Handling.

另請參閱

適用於