I'm trying to optimize a a method that returns the highest bit set in a bit pattern, my current code is :

privateint HighestBitSet(int bitPattern) { return (Convert.ToString(bitPattern, 2).Length - 1) - Convert.ToString(bitPattern, 2).IndexOf("1"); }

I know that in c++ i can use an assembler intruction to do this but in c# is not possible so, how can i optimize this ?
Tnks