How does local initialization with Parallel ForEach work?

Question

I am unsure about the use of the local init function in Parallel.ForEach, as described in the msdn article: http://msdn.microsoft.com/en-us/library/dd997393.aspx

Answer 1

You can get a hint on MSDN in the correct Parallel.ForEach overload.

The localInit delegate is invoked once for each thread that participates in the loop's execution and returns the initial local state for each of those tasks. These initial states are passed to the first body invocations on each task. Then, every subsequent body invocation returns a possibly modified state value that is passed to the next body invocation.

In your example () => 0 is a delegate just returning 0, so this value is used for the first iteration on each task.