I have the following structure

public interface IUser
{
  Guid Id { get; set; }
  string Name { get; set; }
  TUserType GetTypeUser<TUserType>()
        where TUserType : class, IUser;
}

public class UserBase : IUser
{
  public Guid Id { get; set; }
  public string Name { get; set; }
  public GetTypeUser<TUserType>()
  {
    // implement something so that based on the given type return the correct subclass
  }
}

public class FullTimeUser : UserBase, IFullTimeUser
{
  public String FullTimeSpecific { get; set;}
}

public class PartTimeUser : UserBase, IPartTimeUser
{
  public String PartTimeSpecific { get; set;}
}

How do I implement GetTypeUser on the base class so that I would be able to pass in the type of subclass I need so that I get an instance of the correct subclass?