VAR isExtern =（mEnter.MethodImplementationFlags 
和MethodImplAttributes.InternalCall）！= 0; 
 

How do I determine if a method is extern , using reflection?

Sample method:

var mEnter = typeof(System.Threading.Monitor).GetMethod("Exit", BindingFlags.Static | BindingFlags.Public);

var isExtern = (mEnter.MethodImplementationFlags
                    & MethodImplAttributes.InternalCall) != 0;