gistfile1.cs

public class Parallel2
{
    public delegate void ParallelForBodyDelegate(int i, int progress);

    public static void For(int fromInclusive, int toExclusive, ParallelForBodyDelegate body)
    {
        int counter = 0;
        Parallel.For(
            fromInclusive,
            toExclusive,
            i =>
                {
                    int progress = Interlocked.Increment(ref counter);
                    body(i, progress);
                });
    }
}