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    <p>There are a couple of issues in your implementation that I would consider changing.</p> <p>First off, this method:</p> <pre><code>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 ); } </code></pre> <p>This is dangerous - The <em>convention</em> for APIs returning <code>Task</code> or <code>Task&lt;T&gt;</code> is to return a "hot" Task. This means that you should design your APIs to always return a task <em>which is already running</em>.</p> <p>This is to prevent problems, like the one you have in your code above:</p> <pre><code> MyAPI.Run( cts.Token ) .ContinueWith( task =&gt; Console.WriteLine( task.Result.ToString() ) ) .Start(); </code></pre> <p>If you look at this, it can be rewritten as:</p> <pre><code> Task&lt;MyResult&gt; original = MyAPI.Run( cts.Token ); Task second = original.ContinueWith( task =&gt; Console.WriteLine( task.Result.ToString() ) ); second.Start(); </code></pre> <p>Here, you're actually calling Start on the wrong task - not the original task, but the continuation... A typical approach would make "Run" return a hot task, which would allow you to write this as:</p> <pre><code> MyAPI.Run( cts.Token ) .ContinueWith( task =&gt; Console.WriteLine( task.Result.ToString() ) ); </code></pre> <p>Again, this rears its head in your second example, as well. You can <code>Task.Factory.StartNew</code>, and have it look at <code>MyAPI.Run</code>, but never actually call <code>Start</code> on the tasks inside... As such, those tasks <em>will never start and never complete</em>.</p> <p>Second, I would recommend using the new conventions for naming that are showing up in .NET 4.5, just for future proofing. This is to make routines that return <code>Task</code> or <code>Task&lt;T&gt;</code> have the name with an <code>Async</code> suffix. In this case, it would be <code>MyAPI.RunAsync</code>. This will allow your code to look like the framework code that will crop up in the next release of .NET.</p> <p>Finally, in regards to your last question:</p> <blockquote> <p>Does Test2 demonstrate the best way to run many MyAPI.Run tasks in parallel?</p> </blockquote> <p>Actually, if you make the <code>Run</code> method return a running task, this becomes far simpler:</p> <pre><code>public static void Test2() { CancellationTokenSource cts = new CancellationTokenSource(); var task1 = MyAPI.RunAsync(cts.Token); var task2 = MyAPI.RunAsync(cts.Token); Task.Factory.ContinueWhenAll&lt;MyResult&gt;( new[] { task1, task2 }, tasks =&gt; { foreach( var task in tasks ) task.ToString(); }, cts.Token); } </code></pre>
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    1. USReed Copsey
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    1. CORegarding your Test2 rewrite, what happens to exception handling? Specifically, with a Parent/Child arrangement, I would `Try` the parent and catch an `AggergateException` of anything thrown by the children. How would this work in your rewrite?
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    2. CO@nmarler You'd have to handle it in the continuation - you can explicitly wrap a Try/catch around a call to Wait in the continuation to handle errors, if needed.
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    3. COI'm mulling over the concept of only returning 'hot' Tasks. In my app I have a "SequenceManager" object that's responsible for running a handful of Tasks that live in other classes. When the SequenceManager is initialized, it was my intention to compose a Task of sub-object Tasks in a certain arrangement (some sequential to each other, some async). Then, at some point in the future, this "master" Task could be run. I think now that SequenceManager init should be simplified, and instead expose a RunAsync method that will compose the sub-RunAsyncs on the fly. Thanks, your advice is very helpful
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