The type or namespace name 'Entity' does not exist in the namespace 'System.Data'

Hi this post is very misleading, if your reading this 2 years on.

With using EF6 and .net 4.5.1 in VS 2013 I have had to reference the following to get this to work

using System.Data.Entity.Core.EntityClient;

a little different to before,

this is more of a FYI for people that come here for help on newer problems than a answer to the original question

Right-click on the Solution from the Visual Studio Solution Explorer click the Manage Nuget packages for solution and install the EntityFramework