Cannot implicity convert type ‘System.Collections.Generic.List’ to ‘System.Collections.Generic.IList

Having problem on my web api “Cannot implicity convert type IQueryable<> to Generic.List”. I’m getting the data from Entity Framework.
When I put ToList() it return this error: System.Collections.Generic.List’ to ‘System.Collections.Generic.IList<LM_WebApi.Controllers.Items>

Can not connect to Sql database in C# asp mvc application with Entity Framework BUT the same code works with Winform application

First of all, please excuse me if it sounds too rooky. I consider myself novice in MVC applications.
I have ran into a strange problem and there does not seem to be any way out of this, at least so far..I have looked everywhere and left no stone unturned to get it worked. Finally I turned to this forum.
This is my first post, so any mistakes please overlook and guide me.