What is difference between loopstate.Break(), loopState.Stop() and CancellationTokenSource.Cancel()

CancellationToken is used to signal cancellation.

loopState.Break() and loopState.Stop() are used to end execution.

Here's an example

Parallel.For(0, maximum_operations, options, (a, loopState) =>    {        // do work        // cancellationToken.Cancel() should be called externally        if(token.IsCancellationRequested)        {            // cancellation requested - perform cleanup work if necessary            // then call            loopState.Break();            // or            loopState.Stop();        }    });

loopState.Break() means complete all iterations on all threads that are prior to the current iteration on the current thread, and then exit the loop (MSDN).

loopState.Stop() means stop all iterations as soon as convenient (MSDN).

Another way to terminate execution is call token.ThrowIfCancellationRequested(), but you will need to handle the OperationCanceledException exception:

public void MyMethod(){    try    {        Parallel.For(0, maximum_operations, options, (a, loopState) =>        {            // do work            token.ThrowIfCancellationRequested();        });    }    catch (OperationCanceledException)    {        // handle cancellation    }}

All of these methods are valid ways to terminate execution of Parallel.For. Which one you use depends on your requirements.

For example:

• Is it essential to immediately stop all execution when your windows Service is stopped? Then you could use token.ThrowIfCancellationRequested()
• Does your loop deal with IDisposable objects that need cleanup? Then you could use loopState.Break() or loopState.Stop()

Some articles for reference:

• MSDN: Cancellation
• MSDN: How to: Stop or Break from a Parallel.For Loop