Parallel.ForEach Progress

ParallelForEachProgress.cs

SynchronizationContext ctx = SynchronizationContext.Current;

int count = 0;
Parallel.ForEach(collection, (item) =>
{
    ComputeYourStuff(item);
    Interlocked.Increment(ref count);
    ctx.Post(d => { progressBar.Value = count; }, null);
});