How to implement generic GetById() where Id can be of various types
You should remove the constraint on TId from your Repository
class
public abstract class Repository<TEntity, TId> : IRepository<TEntity, TId>
where TEntity : class, IEntity<TId>
{
public virtual TEntity GetById(TId id)
{
return context.Set<TEntity>().Find(id);
}
}
To your 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 an ID of type int, and one of type string.
public virtual TEntity GetById<TId>(TId id)
{
return context.Set<TEntity>().SingleOrDefault(x => x.Id == id);
}
For generic parameter, just make a generic method like above
public interface IEntity<TId> 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<TId>