C# Language: generics, open/closed, bound/unbound, constructed

Question

I\'m reading book \"the C# programming Language\", 4th Edition, by Anders Hejlsberg etc.

There are several definitions that are a bit twisting:

unbo

Answer 1

An excellent answer is given by Jon, here.

Not giving a technical description since everything is there perfectly in the linked answer. To merely replicate the gist of it as an answer here, it would look like:

A                             //non generic, bound
A<U, V>                       //generic,     bound,  open,   constructed
A<int, V>                     //generic,     bound,  open,   constructed
A<int, int>                   //generic,     bound,  closed, constructed
A<,> (used like typeof(A<,>)) //generic,     unbound 

Edited after discussion with Heinzi.

Answer 2

These are examples of unbound generic types:

• List<>
• Dictionary<,>

They can be used with typeof, i.e., the following are valid expressions:

• typeof(List<>)
• typeof(Dictionary<,>)

That should answer your question 2. With respect to question 1, note that type arguments can be constructed types or type parameters. Thus, your list should be updated as follows:

public class MyClass<T, U> {  // declares the type parameters T and U

    // all of these are
    // - generic,
    // - constructed (since two type arguments are supplied), and
    // - bound (since they are constructed):

    private Dictionary<T, U> var1;     // open (since T and U are type parameters)
    private Dictionary<T, int> var2;   // open (since T is a type parameter)
    private Dictionary<int, int> var3; // closed
}