Reading the outcome of parallel loops in .NET C#

The Parallel.For() and Parallel.ForEach() methods both return a ParallelLoopResult object. This object has two properties which you can use to read if Break or Stop have been called:

• IsCompleted: true if all loop iterations have been completed without calling either Break or Stop
• LowestBreakIteration: the index of the lowest iteration in which the Break method was called

Example:

ParallelLoopResult parallelLoopResult =
        Parallel.For(0, 10, (int index, ParallelLoopState parallelLoopState) =>
	{
		if (index == 5)
		{
			parallelLoopState.Stop();
		}
	});

Console.WriteLine("IsCompleted: {0}", parallelLoopResult.IsCompleted);
Console.WriteLine("BreakValue: {0}", parallelLoopResult.LowestBreakIteration.HasValue?       parallelLoopResult.LowestBreakIteration.Value
				: -1);

The properties return the following values:

IsCompleted (IC): false
LowestBreakIteration.HasValue (LBI): false

Here come the possible value pairs and their meaning:

• IC true, LBI false: all iterations were completed without breaking or stopping
• IC false, LBI false: Stop was called
• IF false, LBI true: Break was called

View the list of posts on the Task Parallel Library here.