Generic type constraint on generic type

Question

I have a class like this:

public class Proxy<TClient>()
    where TClient : ClientBase<TChannel>
{

}

I want to be able to specify something like this:

where TClient : ClientBase<TChannel>
where TChannel : class

but without specifying it in the class definition like so:

public class Proxy<TClient, TChannel>()

Is there a way to do this or am I required to have the second type definition as above?

Answer 1

That's not possible. You have to include TChannel as a generic type parameter of Proxy.

One of the options to get over this “limitation” (in quotes because it is a by-design feature that arises from how the C# type system works) is to use an interface which each channel would be supposed to implement:

public interface IChannel { … }

public class Proxy<TClient>()
    where TClient : ClientBase<IChannel>
{ 
}

public class MyObscureChannel : IChannel { … }

public class MyObscureClient : ChannelBase<MyObscureChannel> { … }

…

var client = new Proxy<MyObscureClient>(…); // MyObscureChannel is implied here