How to implement generic GetById() where Id can be of various types

Question

I am trying to implement a generic GetById(T id) method which will cater for types which may have differing ID types. In my example, I have an entity which has

Answer 1

public interface IEntity where TId : class
{
    TId Id { get; set; }
}

The where TId : class constraint requires every implementation to have a Id which derives from object which is not true for value types like int.

Thats what the error message tells you: The type 'int' must be a reference type in order to use it as parameter 'TId' in the generic type of method IEntity

Just remove the constraint where TId : class from IEntity