Get generic parameters from a ByReferenceType with Mono.Cecil

Question

I have a method which gets a parameter such as:

public void Foo(ref Action<string> bar);

Using Cecil to enumerate the parameters yields a ByReferenceType. Calling GetElementType() in an attempt to dereference the parameter returns a TypeReference with fullname:

System.Action`1

Somehow it has lost the generic parameters, and is no longer a GenericInstanceType.

How can I properly dereference the byref parameter, and get to the actual generic instance type?

Answer 1

You can dive into the TypeSpec using this (you can of course make it shorter when you know what you're after):

ParameterDefinition parameter = ...;
ByReferenceType byref = (ByReferenceType) parameter.ParameterType;
GenericInstanceType action_string = (GenericInstanceType) byref.ElementType;
TypeReference action = action_string.ElementType;
TypeReference str = action_string.GenericArguments [0];

The GetElementType method returns the original element type from which the TypeSpec is constructed.