Using Reflection to detect if the Implementation of a given Method has changed

I am using reflection to find classes implementing a certain interface in a given assembly. Then I instantiate those classes and execute a given method of said interface.

Now I want to be able to create some sort of checksum of the methods actual implementation details and save that to disk so that I can later use it to detect if the method implementation has been changed since the method was last executed (after a recompile).

I looked thoroughly at the MethodInfo class but can't see any way of obtaining information on the implementation details. Am I on the wrong path? I'm using .Net Core 3.1 and C#.