title: Update record if it exists
body: <p>I'm new to EF, and I'm trying to understand the best way to handle inserting and updating data. Just for some context, I'm using the .net mvc website boiler plate, and I've created a customers table with a 1:1 relationship to aspnetusers. I've created a view to manage customer data. </p>
  
  <p>Here is my HttpPost ActionResult:</p>
  
  <pre><code>    [HttpPost]
      [ValidateAntiForgeryToken]
      public async Task&lt;ActionResult&gt; AddCard(External.Stripe.Customer customer)
      {
          if (!ModelState.IsValid)
          {
              return View(customer);
          }
  
          External.Stripe.CustomerOperations co = new External.Stripe.CustomerOperations();
          customer = co.Create(customer);
  
          var user = UserManager.FindById(User.Identity.GetUserId());
          customer.UserId = user.Id;
  
          var context = new External.Stripe.CustomerContext();
  
  
          context.Customers.Add(customer);
          context.SaveChanges();
  
          return RedirectToAction("Index", "Manage");
      }
  </code></pre>
  
  <p>I feel like I'm going down the wrong path, because if I make any updates to the customer  model, I actually need to check EF if my key already exists, and if it does, run an update instead. I figured EF would have a native way of saving my model if it needs to be updated. I also don't know if this is even where I would persist my model, or if it is better placed somewhere else in my code.</p>