Question

After calling a function, which returns an object, I try to store the value on stack in a local variable and then push it back, but it fails with an exception

Exception has been thrown with a target of invocation

Code is as follows:

.....

MethodInfo checked_static = typeof(NameSpace1.Class1).GetMethod(
    "Check", new Type[1] { typeof(object) });
adderIL.Emit(OpCodes.Callvirt, checked_static);
adderIL.Emit(OpCodes.Stloc_3);
adderIL.Emit(OpCodes.Ldloc_3);
adderIL.Emit(OpCodes.Brfalse, TRUE);

.....

If I remove Stloc_3 and Ldloc_3 everything works fine, I am lost here.

Answer 1

Based on your response to my question, it appears that you haven’t declared your local. Each method in IL indicates the types of all of the locals that it uses, so you need to declare it using one of the DeclareLocal overloads on your adderIL instance. If you haven’t declared any other locals, then you’ll also need to use OpCodes.Stloc_0 instead of OpCodes.Stloc_3 (and likewise for the loads); alternatively you can just use OpCodes.Stloc or OpCodes.Stloc_S and pass the LocalBuilder instance from the DeclareLocal call as the second argument to adderIL.Emit (in which case the Reflection.Emit library will get the correct index from the local for you).