We have an Intranet site we are developing in ASP.NET 5 aka vNext and MVC 6. 

We'd like to be able to get the Windows Network ID the user is logged in as, but then there is an existing database defining roles, etc. we were going to leverage and have already done so. Really all I want to do is get the Windows user ID while using ASP.NET Identity to manage roles the user has access to. Any suggestions how to accomplish this?

Essentially in Startup.cs I have something like below in Configure Services: 

```
    services.AddIdentity<WorldUser, IdentityRole>(config =>
    {
       config.User.RequireUniqueEmail = true;
       config.Password.RequiredLength = 8;
    }).AddEntityFrameworkStores<WorldContext>();

```

Next in Configure I have: app.UseIdentity();

Windows Authentication is on at the project properties level and so is Anonymous. I see no way to actually get the Windows User ID.