ECall methods must be packaged into a system module

This code

[MethodImpl(MethodImplOptions.InternalCall)] public extern static IntPtr GetFunctionPointer_;

public static void Main {           Console.WriteLine("\n\n---\n\n"); GetFunctionPointer_; }

will compile OK but throw this error:

Unhandled Exception: System.Security.SecurityException: ECall methods must be packaged into a system module.

Note: changing the MSIL to GetFunctionPointer; so that we are calling the correct internal function name GetFunctionPointer (versus GetFunctionPointer_), throws the same error ( GetFunctionPointer will not compile). Executing from Partial trust throws the same error since Peverify finds no issues with it.

This makes sense since if this was possible, there would be dozens of ways to bypass the CLR Security Measures