NuGet add reference error while installing packages

Question

I am not able to install any package by Nuget. For example when I want install entity framework I receive following error:

install-package EntityFramework
Su         


        

Answer 1

After updating my Visual Studio 2015 nuget stopped working.

After reading the posted solutions I founded that's a know bug, see http://blog.nuget.org/20150226/nuget-3.0-beta2.html

From Visual Studio I unistalled nuget extension, closed visual studio , downloaded and installed latest nuget version from https://dist.nuget.org/index.html

It worked