I am trying to build a sample application using EF7 and mvc 6 in visual studio 2015 pre release.
While installing both EF7 and MVC6 using package manager console getting
I had a similar issue in Visual Studio 2015 Community Edition.
Created a simple ASP.NET MVC 5 default project that I hosted on Azure. I was working through the project and when I tried to load up the NuGet GUI but kept getting the "Object Reference..." error.
I restarted Visual Studio in Administrator mode (right-clicked Visual Studio and started in Administrator mode) which resolved the problem.