title: How to update model in the database, from asp.net MVC2, using Entity Framework?
body: <p>I'm building ASP.NET MVC2 application, and using Entity Framework as ORM. I am having troubles updating object in the database. Every time I try entity.SaveChanges(), EF inserts new line in the table, regardless of do I want update, or insert to be done. I tried attaching (like in this next example) object to entity, but then I got </p>
  
  <pre><code>{"An object with a null EntityKey value cannot be attached to an object context."}
  </code></pre>
  
  <p>Here's my simple function for inserts and updates (it's not really about vehicles, but it's simpler to explain like this, although I don't think that this effects answers at all)...</p>
  
  <pre><code>        public static void InsertOrUpdateCar(this Vehicles entity, Cars car)
      {
          if (car.Id == 0 || car.Id == null)
          {
              entity.Cars.AddObject(car);
          }
          else
          {
              entity.Attach(car);
          }
          entitet.SaveChanges();
      }
  </code></pre>
  
  <p>I even tried using AttachTo("Cars", car), but I got the same exception.</p>
  
  <p>Anyone has experience with this?</p>