Question

Basically, what I want to do, is:

public class MySpecialCollection<T>
    where T : ISomething { ... }

public interface ISomething
{
    public ISomething NextElement { get; }
    public ISomething PreviousElement { get; }
}

public class XSomething : ISomething { ... }

MySpecialCollection<XSomething> coll;
XSomething element = coll.GetElementByShoeSize(39);
XSomething nextElement = element.NextElement; // <-- line of interest

… without having to cast nextElement to XSomething. Any ideas?
I would have wanted something in the kind of …

public interface ISomething
{
    public SameType NextElement { get; }
    public SameType PreviousElement { get; }
}

Thank you in advance!

Answer 1

Make the interface generic:

public class MySpecialCollection<T> where T : ISomething<T> {
  ...
}

public interface ISomething<T> {
  T NextElement { get; }
  T PreviousElement { get; }
}

public class XSomething : ISomething<XSomething> {
  ...
}