The type must be a reference type in order to use it as parameter T in the generic type or method

Question

I m getting deeper into generics and now have a situation I need help with  I get a compile error on the  Derived  class below as shown in the subject title  I see many other posts similar to this one but I m not seeing the relationship  Can someone tell me how to resolve this   using System  using System Collections Generic    namespace Example       public class ViewContext               ViewContext                  public interface IModel                  public interface IView lt T gt  where T   IModel                ViewContext ViewContext   get  set               public class SomeModel   IModel               public SomeModel               public int ID   get  set               public class Base lt T gt  where T   IModel                public Base IView lt T gt  view                                 public class Derived lt SomeModel gt    Base lt SomeModel gt  where SomeModel   IModel                public Derived IView lt SomeModel gt  view                base view                        SomeModel m    SomeModel Activator CreateInstance typeof SomeModel                Service lt SomeModel gt  s   new Service lt SomeModel gt                 s Work m                        public class Service lt SomeModel gt  where SomeModel   IModel               public Service                                public void Work SomeModel m

User · Answer

You get this error if you have constrained T to being a class

User · Answer

I can t repro  but I suspect that in your actual code there is a constraint somewhere that T   class - you need to propagate that to make the compiler happy  for example  hard to say for sure without a repro example    public class Derived lt SomeModel gt    Base lt SomeModel gt  where SomeModel   class  IModel                                                                                                                                            see this bit

User · Answer

If you put constrains on a generic class or method  every other generic class or method that is using it need to have  at least  those constrains

[c#] The type must be a reference type in order to use it as parameter 'T' in the generic type or method

Examples related to c#

Examples related to generics