title: Using AutoMapper in the Edit action method in an MVC3 application
body: <p>Here is my controller code, which works 100% as I need it to. However the POST method isn't using the AutoMapper and that is not OK. How can I use AutoMapper in this action method?</p>
  
  <p>I'm using Entity Framework 4 with the Repository Pattern to access data.</p>
  
  <pre><code>public ActionResult Edit(int id)
  {
      Product product = _productRepository.FindProduct(id);
      var model = Mapper.Map&lt;Product, ProductModel&gt;(product);
      return View(model);
  }
  
  [HttpPost]
  public ActionResult Edit(ProductModel model)
  {
      if (ModelState.IsValid)
      {
          Product product = _productRepository.FindProduct(model.ProductId);
  
          product.Name = model.Name;
          product.Description = model.Description;
          product.UnitPrice = model.UnitPrice;
  
          _productRepository.SaveChanges();
  
          return RedirectToAction("Index");
      }
  
      return View(model);
  }
  </code></pre>
  
  <p>If I use AutoMapper, the entity framework reference is lost and the data doesn't persist to the database.</p>
  
  <pre><code>[HttpPost]
  public ActionResult Edit(ProductModel model)
  {
      if (ModelState.IsValid)
      {
          Product product = _productRepository.FindProduct(model.ProductId);
          product = Mapper.Map&lt;ProductModel, Product&gt;(model);
  
          _productRepository.SaveChanges();
  
          return RedirectToAction("Index");
      }
  
      return View(model);
  }
  </code></pre>
  
  <p>I'm guessing this is caused the Mapper.Map function returning a brand new Product object and because of that, no references to the entity framework graph is being kept. What alternatives do you suggest?</p>