Question

I have a object[] containig some values. I want to extract infomation out of it, but I fail at casting the second object in the array (a WeakReference) to a IList with T as the third value in the array.

Take a look at my code:

object[] vals = GetValues(); //vals[2] = WeakReference, vals[3] = Type of T, vals[4] = index in the list
IList<((Type)vals[3])> list = (IList<((Type)vals[3])>)(((WeakReference)vals[2]).Target); //This line does not even compile, seems like I'm doing something wrong..
object oo = list.ElementAt((int)vals[4]);
//Do something with oo...

Any suggestions how I can cast the Target of the WeakReference to a IList interface with T = vals[3] ?

Answer 1

It’s really strange that you are packing so much heterogeneous information into an array. Arrays are normally used to store elements of the same type. Why not encapsulate the data in a proper type?

But to answer the question as asked – in C# 4, you can use dynamic:

var target = ((dynamic)vals[2]).Target;

if(target != null)
{
    object oo = Enumerable.ElementAt(target, vals[4]);
    //Do something with oo...
}

(EDIT: If you want to minimize the use of dynamic here, cast to a WeakReference and leave the dynamic call to the end. This way, type-safety is ‘maximized’.)

Otherwise, you can use reflection:

object target = ((WeakReference)vals[2]).Target;

if (target != null)
{
    object oo = target.GetType()
                      .GetProperty("Item")
                      .GetValue(target, new[] { vals[4] });
    //Do something with oo...
}

(EDIT: If the indexer could be explicitly implemented, you’ll probably need to use the interface mappings.)