What is the reason behind this huge Performance difference in .Net 4

Question

I was just doing some research on RedBlack Tree. I knew that SortedSet class in .Net 4.0 uses RedBlack tree. So I took that part out as is using Reflector and created a RedBlack

Answer 1

SortedSet includes a TargetedPatchingOptOut attribute, did your copied version include that?

[TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
public bool Add(T item)
{
    return this.AddIfNotPresent(item);
}