ASP.NET (OWIN) Identity: How to get UserID from a Web API controller?

You should be able to get user id on both MVC controller and web api controller by same extension method in identity 1.0 RTW package.

Here is the extensions from identity package:

namespace Microsoft.AspNet.Identity
{
    public static class IdentityExtensions
    {
        public static string FindFirstValue(this ClaimsIdentity identity, string claimType);
        public static string GetUserId(this IIdentity identity);
        public static string GetUserName(this IIdentity identity);
    }
}

The IIdentity is the base interface for all identity types. You may need to add "using Microsoft.AspNet.Identity" in order to see the extension method.

BTW: regarding adding a foreign table for user, why not using ApplicationUser and add navigation property to UserPreference to let EF to handle their relationship? That will be easier.

ClaimsIdentity identity = new ClaimsIdentity(OAuthDefaults.AuthenticationType);
identity.AddClaim(new Claim(ClaimTypes.Name, userName));
identity.AddClaim(new Claim(ClaimTypes.NameIdentifier, UserID));

ClaimTypes.NameIdentifier is the claim for the function User.Identity.GetUserId()