[Solved] Why do I get Argument exception when I try to use “Include(“PropertyName”)” in query EF?

Question

I solved the problem. Actually the problem was I didn’t have a using directive to System.Data.Entity namespace at the top of my class.

Even thought I could use "Include("PropertyName)" name in my query, I couldn’t use "Include(x=> x.Childs)". But after adding "using System.Data.Entity" on top of my class I can use "Include" in these both ways on a query and my error is solved.

Accepted Answer

I solved the problem. Actually the problem was I didn’t have a using directive to System.Data.Entity namespace at the top of my class.

Even thought I could use "Include("PropertyName)" name in my query, I couldn’t use "Include(x=> x.Childs)". But after adding "using System.Data.Entity" on top of my class I can use "Include" in these both ways on a query and my error is solved.