Proper way to get current User ID in Entity Framework Core

Question

There are a bunch of different answers floating around here for the different RC\'s of ASP.NET Core on how to get the ID of the currently logged in user. I wanted to ask the def

Answer 1

If you are accessing this from withing the Controller, then using UserManager to get the user ID is pretty inefficient as you are making a round trip to the database. If you are using ClaimsIdentity, you can do something like this to get the user id:

var claimsIdentity = (ClaimsIdentity)this.User.Identity;
var claim = claimsIdentity.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier);
var userId = claim.Value;

This method just reads the user ID which is already present in the cookie, which in turn is automatically deserialized and stored in a ClaimsIdentity instance.

I use this helper class:

public static class UserHelpers
{
    public static string GetUserId(this IPrincipal principal)
    {
        var claimsIdentity = (ClaimsIdentity)principal.Identity;
        var claim = claimsIdentity.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier);
        return claim.Value;
    }
}

So getting a user ID becomes:

var userId = this.User.GetUserId();

If, for some reason, the required claim is not present in the Claims colleciton, you can easily add it when creating the user's ClaimsIdentity:

public class ApplicaionUser : IdentityUser
{
    public async Task GenerateUserIdentityAsync(UserManager manager)
    {
        var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
        userIdentity.AddClaim(new Claim(ClaimTypes.NameIdentifier, this.UserId));
        return userIdentity;
    }
}