I am Getting Error Error 'System.Linq.IQueryable

Question

public ActionResult Login(UserResgitartion objUser)

{

if (ModelState.IsValid)

{

using (MyDatabaseEntities Db = new MyDatabaseEntities())

{

var obj = Db.UserResgitartions.Where(a => a.UserName.Equals(objUser.UserName));

if(obj != null)

{

// Error here in userId and UserName  

Session["UserID"]= obj.UserId.ToString();

Session["USERNAME"] = obj.UserName.ToString();

return RedirectToAction("UserDashBoard");

}

}

}

return View(objUser);

}