How to authenticate user without login

Question

Is it possible to authenticate user under the standard ASP .NET MVC4 project using only UserId so we can skip the code below?

[HttpPost]
[AllowAnonymous]
[ValidateAntiForgeryToken]
public ActionResult Login(LoginModel model, string returnUrl)
{
    if (ModelState.IsValid && WebSecurity.Login(model.UserName, model.Password, persistCookie: model.RememberMe))
    {

Answer 1

Ok here is the solution

var userId = "123";

using (UsersContext db = new UsersContext())
{
   UserProfile userProfile = db.UserProfiles.FirstOrDefault(u => u.UserId == userId);
   FormsAuthentication.SetAuthCookie(userProfile.UserName, false);
}