I am trying to use Authentication Plugin of ServiceStack. I added NuGet packages for ServiceStack 4.0.11 but I am unable to find DLL ServiceStack.ServiceInterface which contains the AuthService and Auth classes. I think Authentication Plugin is dependent on this DLL. How can i add ServiceStack.ServiceInterface to my project?
Sounds like you might have a version mismatch. That dll has been merged to the main one. Per ServiceStack v4 release notes:
ServiceStack.Interfaces NuGet project created and ServiceInterface has been merged into ServiceStack