Question

Recently I have read a term “naked type constraint” in the context of Generics. What does it
mean? Where do we use it?

Answer 1

From MSDN:

Constraint          Description

where T : U         The type argument supplied for T must be or derive from
                    the argument supplied for U. This is called a naked type
                    constraint.

When a generic type parameter is used as a constraint, it is called a naked type constraint. Naked type constraints are useful when a member function with its own type parameter has to constrain that parameter to the type parameter of the containing type, as shown in the following example:

class List<T>
{
    void Add<U>(List<U> items) where U : T {/*...*/}
}