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copied!<p>The best way is to use the <code>Task Parallel Library (TPL)</code> and <code>Continuations</code>. A continuation not only allows you to create a flow of tasks but also handles your exceptions. This is a <a href="http://www.codeproject.com/Articles/152765/Task-Parallel-Library-1-of-n" rel="nofollow">great introduction</a> to the TPL. But to give you some idea...</p> <p>You can start a TPL task using </p> <pre><code>Task task = Task.Factory.StartNew(() => { // Do some work here... }); </code></pre> <p>Now to start a second task when an antecedent task finishes (in error or successfully) you can use the <code>ContinueWith</code> method</p> <pre><code>Task task1 = Task.Factory.StartNew(() => Console.WriteLine("Antecedant Task")); Task task2 = task1.ContinueWith(antTask => Console.WriteLine("Continuation...")); </code></pre> <p>So as soon as <code>task1</code> completes, fails or is cancelled <code>task2</code> 'fires-up' and starts running. Note that if <code>task1</code> had completed before reaching the second line of code <code>task2</code> would be scheduled to execute immediately. The <code>antTask</code> argument passed to the second lambda is a reference to the antecedent task. See <a href="http://www.albahari.com/threading/" rel="nofollow">this link</a> for more detailed examples...</p> <p>You can also pass continuations results from the antecedent task</p> <pre><code>Task.Factory.StartNew<int>(() => 1) .ContinueWith(antTask => antTask.Result * 4) .ContinueWith(antTask => antTask.Result * 4) .ContinueWith(antTask =>Console.WriteLine(antTask.Result * 4)); // Prints 64. </code></pre> <p>Note. Be sure to read up on exception handling in the first link provided as this can lead a newcomer to TPL astray.</p> <p>One last thing to look at in particular for what you want is child tasks. Child tasks are those which are created as <code>AttachedToParent</code>. In this case the continuation will not run until all child tasks have completed</p> <pre><code>TaskCreationOptions atp = TaskCreationOptions.AttachedToParent; Task.Factory.StartNew(() => { Task.Factory.StartNew(() => { SomeMethod() }, atp); Task.Factory.StartNew(() => { SomeOtherMethod() }, atp); }).ContinueWith( cont => { Console.WriteLine("Finished!") }); </code></pre> <p>I hope this helps.</p> <p><em>Edit: Have you had a look at <a href="http://msdn.microsoft.com/en-us/library/system.collections.concurrent.aspx" rel="nofollow"><code>ConcurrentCollections</code></a> in particular the <code>BlockngCollection<T></code>. So in your case you might use something like</em></p> <pre><code>public class TaskQueue : IDisposable { BlockingCollection<Action> taskX = new BlockingCollection<Action>(); public TaskQueue(int taskCount) { // Create and start new Task for each consumer. for (int i = 0; i < taskCount; i++) Task.Factory.StartNew(Consumer); } public void Dispose() { taskX.CompleteAdding(); } public void EnqueueTask (Action action) { taskX.Add(Action); } void Consumer() { // This seq. that we are enumerating will BLOCK when no elements // are avalible and will end when CompleteAdding is called. foreach (Action action in taskX.GetConsumingEnumerable()) action(); // Perform your task. } } </code></pre>

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