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POExpose a cancellable Task
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  1. POExpose a cancellable Task
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    copied!<p>I'm designing an API that exposes a cancellable <code>Task</code>, and want to make sure I have designed it correctly. Is there a standard pattern for exposing <code>Task</code>s (maybe something similar to the APM BeginXxx/EndXxx pattern)? Any suggestions to improve? See <code>MyAPI.Run</code></p> <p>Does <code>Test2</code> demonstrate the best way to run many <code>MyAPI.Run</code> tasks in parallel?</p> <pre><code>public static class MyAPI { public static Task&lt;MyResult&gt; Run( CancellationToken token ) { // lazily create Task, so as to include the specified CancellationToken return new Task&lt;MyResult&gt;( MyPrivateAsyncMethod, token, token ); } private static MyResult MyPrivateAsyncMethod( object state ) { CancellationToken ct = (CancellationToken)state; ct.ThrowIfCancellationRequested(); return new MyResult(); } } public static class TestMyAPI { // User can start the Task directly public static void Test1() { CancellationTokenSource cts = new CancellationTokenSource(); MyAPI.Run( cts.Token ) .ContinueWith( task =&gt; Console.WriteLine( task.Result.ToString() ) ) .Start(); } // User must wrap in new Tasks to get Parent/Child relationship public static void Test2() { CancellationTokenSource cts = new CancellationTokenSource(); Task.Factory.StartNew( () =&gt; { var childTasks = new[] { Task.Factory.StartNew&lt;MyResult&gt;( () =&gt; MyAPI.Run( cts.Token ).Result, cts.Token, TaskCreationOptions.AttachedToParent, TaskScheduler.Default ), Task.Factory.StartNew&lt;MyResult&gt;( () =&gt; MyAPI.Run( cts.Token ).Result, cts.Token, TaskCreationOptions.AttachedToParent, TaskScheduler.Default ) }; Task.Factory .ContinueWhenAll&lt;MyResult&gt;( childTasks, tasks =&gt; { foreach( var task in tasks ) task.ToString(); } ) .Start(); }, cts.Token ); } } </code></pre>
 

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