Dynamically Create a generic type for template

Question

I'm programming WCF using the ChannelFactory which expects a type in order to call the CreateChannel method. For example:

IProxy proxy = ChannelFactory<IProxy>.CreateChannel(...);

In my case I'm doing routing so I don't know what type my channel factory will be using. I can parse a message header to determine the type but I hit a brick wall there because even if I have an instance of Type I can't pass that where ChannelFactory expects a generic type.

Another way of restating this problem in very simple terms would be that I'm attempting to do something like this:

string listtype = Console.ReadLine(); // say "System.Int32"
Type t = Type.GetType( listtype);
List<t> myIntegers = new List<>(); // does not compile, expects a "type"
List<typeof(t)> myIntegers = new List<typeof(t)>(); // interesting - type must resolve at compile time?

Is there an approach to this I can leverage within C#?

Answer 1

What you are looking for is MakeGenericType

string elementTypeName = Console.ReadLine();
Type elementType = Type.GetType(elementTypeName);
Type[] types = new Type[] { elementType };

Type listType = typeof(List<>);
Type genericType = listType.MakeGenericType(types);
IProxy  proxy = (IProxy)Activator.CreateInstance(genericType);

So what you are doing is getting the type-definition of the generic "template" class, then building a specialization of the type using your runtime-driving types.