Question

I customize IIdentity and IPrincipal adding a few more properties in IIdentity.

You can obtain a strongly typed instance @User.Identity for my custom class? Without having to make conversions in cast.

I thought of something like razor customize the View, but do not even know where to start.

Answer 1

You could try creating an extension method on IPrincipal

public static class PrincipalExtensions
{
    public static MyIdentity GetMyIdentity (this IPrincipal principal)
    {
        return principal.Identity as MyIdentity;
    }
}

and then get your identity by calling @User.GetMyIdentity()