Is there a reasonable approach to “default” type parameters in C# Generics?

Question

In C++ templates, one can specify that a certain type parameter is a default. I.e. unless explicitly specified, it will use type T.

Can this be done or approximated

Answer 1

One solution is subclassing. Another one I would use instead, is factory methods (combined with var keyword).

public class MyTemplate
{
     public MyTemplate(..args..) { ... } // constructor
}

public static class MyTemplate{

     public static MyTemplate Create(..args..)
     {
         return new MyTemplate(... params ...);
     }

     public static MyTemplate Create(...args...)
     {
         return new MyTemplate(... params ...);
     }
}

var val1 = MyTemplate.Create();
var val2 = MyTemplate.Create();

In the above example val2 is of type MyTemplate and not a type derived from it.

A type class MyStringTemplate:MyTemplate is not the same type as MyTemplate. This could pose some problems in certain scenarios. For instance you can't cast an instance of MyTemplate to MyStringTemplate.