ERROR

heyy buddy!

that namespace n dll are already in my project snippet.

instead of using .Add()use .AddObject() and instead of using .Remove use .DeleteObject()..


The add and remove are from EntityFrame namespace System.Data.Entity

so my guess is using System.Data.Entity missing ? Also check reference EntityFramework.dll added in project ? Or use package manager (nuget) to get EF added in project?, Does your context derive from DBContext ? If not No add. If you see AddObject, you are most likely deriving from ObjectContext instead