Task.Factory.StartNew vs new Task

c# c#-4.0 asynchronous
Ned Stoyanov picture Ned Stoyanov · Feb 28, 2014 · Viewed 34.9k times · Source

Does anyone know if there is any difference between doing Task.Factory.StartNew vs new Task followed by calling Start on the task. Looking at reflector there doesn't seem to be much difference. So perhaps the only difference is that Task.Factory.StartNewreturns a task that is already started. Is this correct?

I know that Task.Factory.StartNewand Task.Run have different default options and Task.Run is the preferred option for .Net 4.5.

Answer

Ned Stoyanov picture Ned Stoyanov · Feb 28, 2014

I found this great article by Stephen Toub, which explains that there is actually a performance penalty when using new Task(...).Start(), as the start method needs to use synchronization to make sure the task is only scheduled once.

His advice is to prefer using Task.Factory.StartNew for .net 4.0. For .net 4.5 Task.Run is the better option.

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