TPL - Difference between MaxDegreeOfParallelism and MaximumConcurrencyLevel

Question

What's the difference between ParallelOptions.MaxDegreeOfParallelism and ParallelOptions.TaskScheduler.MaximumConcurrencyLevel? When would you use either?

Answer 1

Using reflector, I've gathered that both are used in EffectiveMaxConcurrencyLevel property:

internal int EffectiveMaxConcurrencyLevel
{
    get
    {
        int maxDegreeOfParallelism = this.MaxDegreeOfParallelism;
        int maximumConcurrencyLevel = this.EffectiveTaskScheduler.MaximumConcurrencyLevel;
        if ((maximumConcurrencyLevel > 0) && (maximumConcurrencyLevel != 0x7fffffff))
        {
            maxDegreeOfParallelism = (maxDegreeOfParallelism == -1) ? maximumConcurrencyLevel : Math.Min(maximumConcurrencyLevel, maxDegreeOfParallelism);
        }
        return maxDegreeOfParallelism;
    }
}