Question

I learning about writing my own interfaces and came across the MSDN article “Interfaces (C# Programming Guide)“. Everything seems fine, except: what does <T> mean or do?

interface IEquatable<T>
{
    bool Equals(T obj);
}

Answer 1

It means that it is a generic interface.

You could create an interface like this:

public interface IMyInterface<T>
{
    T TheThing {get; set;}
}

and you could implement it in various ways:

public class MyStringClass : IMyInterface<string>
{
    public string TheThing {get; set;}
}

and like this:

public class MyIntClass : IMyInterface<int>
{
    public int TheThing {get; set;}
}