ASP.NET MVC 3 Save and edit from the same form - asp.net-mvc

Question

We have a form and depending upon the circumstances we want to switch between an add operation and an update operation from the same form. Below is a cut down version of our form.
Effectively the "Order number" textbox is disabled and can never be edited in this form. Now, the scenario is a bit like this:
The first time the user lands on this form, the "Order number" text box is blank.
The user enters a customer name and submits the form.
At this point in the controller action, we get the max value of order number in the database and increment the order number by 1 . We then add that new record in the database.
If that operation is successful, we update the current form and the "Order Number" textbox should now be updated with the order number created in the previous step AND also what should happen is that we are now in Edit mode.
Say the user then updates the "Customer name" and submits the form, the record in the database should be updated in this instance.
Now for some code:
The View:
<%: Html.TextBox("OrderNumber", Model.OrderNumber == 0 ? "" : Model.OrderNumber.ToString(), new { #disabled = "true" })%>
The controller:
public ActionResult Index()
{
var customerOrderModel = new CustomerOrderModel();
return View(customerOrderModel);
}
public ActionResult Add(CustomerOrderModel customerOrderModel, FormCollection values)
{
// We write the logic for either the add or update.
return this.View("Index", customerOrderModel);
}
I have removed the code from the Add action because from putting breakpoints we know that the "// We write the logic for either the add or update." is not the problem.
Now where we are having trouble is this. We can add the new entry in the table following which the "Order Number" field gets updated and is displayed correctly. However, after we change the customer name and try to update, the customerOrderModel passed into the "Add" action shows that the order number being passed is 0(which is our default in the system and which is used to determine if we are performing an add or update operation).
So the question is why is our textbox getting updated, which would seem to indicate that our model is getting updated, but then when we try to submit, the correct model doesn't get passed in? Moreover, why is it that the Index action doesn't get hit after the "Add" action is completed? What do we have to do to get things to work the way we want them to?

Answer 1

Model
namespace Demo.Models
{
public class Order
{
public int OrderId { get; set; }
public string CustomerName { get; set; }
}
public class OrderDb:DbContext
{
public DbSet<Order> Orders { get; set; }
}
}
View
#model Demo.Models.Order
<form action="/" method="post">
<table>
<tr>
<td>#Html.LabelFor(m=>m.OrderId)</td>
<td>
#Html.EditorFor(m => m.OrderId)
</td>
</tr>
<tr>
<td>
#Html.LabelFor(m=>m.CustomerName)
</td>
<td>
#Html.EditorFor(m=>m.CustomerName)
</td>
</tr>
<tr>
<td></td>
<td>
<input type="submit" name="submit" value="submit" />
</td>
</tr>
</table>
</form>
Action
public ActionResult Index(Order o)
{
if (o.CustomerName != null)
{
using (OrderDb db = new OrderDb())
{
db.Entry(o).State = o.OrderId == 0 ? EntityState.Added : EntityState.Modified;
db.SaveChanges();
ModelState.Clear();
}
}
return View(o);
}

Answer 2

This is because HtmlHelpers look to ModelState for values first and then uses the values you explicitly use.
So when you add the entity you get ["Id"]=0 inside your model state.
So solve you have to clear your ModelState with .Clear() after a successful add.