[mono-cecil] How to create a generic instance

[seesharper]

Hi!

I don't understand how to emit the code to create an instance of a
generic type.

Mono.Cecil 0.9.4.0


I will illustrate this with a very simple example.

This is the code that I want to emit.

       public void TestNull(int value)
        {
            Nullable<int> test = value;
        }

NOTE:

I don't know that the generic argument is an int at the time of
emitting the code.

I need to read the parameter type and create a Nullable<T> according
to the parameter type.

This means that I CAN'T do something like:

MethodReference ctor = _moduleDefinition.Import(typeof
(Nullable<int>).GetConstructor(new Type[] {typeof (int)}));


This is the IL code that needs to be emitted.

    .maxstack 2
    .locals init (
        [0] valuetype [mscorlib]System.Nullable`1<int32> test)
    L_0000: nop
    L_0001: ldloca.s test
    L_0003: ldarg.1
    L_0004: call instance void
[mscorlib]System.Nullable`1<int32>::.ctor(!0)
    L_0009: nop
    L_000a: ret


So this is what I got so far.

First a create a GenericInstanceType:

var nullableType = _moduleDefinition.Import(typeof(Nullable<>));
var genericType =
nullableType.MakeGenericInstanceType(_moduleDefinition.Import(typeof(int)));

(yeah, I used the Cecil.Rocks extension method for creating the
generic instance type, but that is not the issue here.)

The int would be the type from the value parameter of the TestNull
method.

Now I have a GenericInstanceType that represents Nullable<int>.

But how do I create a MethodReference that represents the constructor
passed to OpCodes.NewObj?

The GenericInstanceType which is derived from MethodReference does not
have a collection of methods so I can't get it from there either.

Next I tried something like this:

MethodReference constructorReference = new MethodReference(".ctor",
_moduleDefinition.Import(typeof(void)), genericType);

No luck on this either.

A lot of forum posts suggests that the methodreference should be added
to the MemberReferences collection of the module.

But that is a read-only collection available from the
GetMemberReferences method.



I must be missing something?

Any help on this issue would be great!!!

Regards

Bernhard Richter














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