How to use the "where" keyword in C# with a generic interface, and inheritance

Question

What I want to achieve is this:

• Declare a generic class (<T>),
• Have the "T" restricted to types that implement IMySpecialInterface<X> (where "X" is not a known type),
• And have the class inherit from a parent class.

to give an incorrect example:

public class MyClass<T> : MyParentClass where T : IMySpecialInterface<X>
{
...
}

What is the proper syntax to achieve this?

Thanks.

Answer 1

You will need to define a non-generic version of IMySpecialInterface<X>, unless you supply a secondary type for MyClass. The whole thing would look like this then:

public interface IMySpecialInterface
{
}

public interface IMySpecialInterface<X> : IMySpecialInterface
{
}

public MyClass<T> : MyParentClass where T : IMySpecialInterface
{
}

Answer 2

You can't use generics without knowing the types, unless you created the type at runtime.

Your best fit would be:

public class MyClass<T, U> : MyParentClass where T: IMySpecialInterface<U>
{

}

UPDATE or could you potentially use dynamic?

Answer 3

public class MyClass<T, X> : MyParentClass where T : IMySpecialInterface<X>
{
...
}