What does it mean when angle brackets are used after an interface?

Question

My sample code has the following:

public class IdentityUser : IdentityUser<string, IdentityUserLogin, IdentityUserRole, IdentityUserClaim>, 
    IUser, 
    IUser<string>
{

I understand that the IdentityUser must implement the IUser methods but can someone explain what it means:

IdentityUser<string, IdentityUserLogin, IdentityUserRole, IdentityUserClaim>

Answer 1

The angle brackets are notation for generics. I recommend reading documentation on C# generics, such as http://msdn.microsoft.com/en-us/library/ms379564(v=vs.80).aspx .

Wherever IdentityUser is defined is something similar to this:

public interface IdentityUser<A,B,C,D> {
  // ...
}

So if you make the following class:

public class MyClass : IdentityUser<string, string, string, string> {
  // ...
}

Then it is saying that MyClass implements IdentityUser and that the type variable A is string , the type variable B is string , and so on.

Answer 2

That is not easy to explain, but it means that the type is a generic one. You should read the relevant topic in the MSDN library for details or maybe the Wikipedia article for an overview of the concept in general.