can't debug DLL

 when one dll is loaded by this way :

byte[ bs = File.ReadAllBytes(filename);
Assembly assembly = Assembly.Load(bs);

In this dll class library project ,I have set on breakpoint, then, I start this project by starting outside program,but cann't stop at this breakpoint.

BUT,by this way

Assembly assembly = Assembly.LoadFile(filename);

it can stop at this breakpoint. It is very strange!! In Visual studio ,the two ways can both stop at the breakpoint.