Asp.Net MVC 2: How exactly does a view model bind back to the model upon post back?

Question

Sorry for the length, but a picture is worth 1000 words:

In ASP.NET MVC 2, the input form field "name" attribute must contain exactly the syntax below that you would use to reference the object in C# in order to bind it back to the object upon post back. That said, if you have an object like the following where it contains multiple Orders having multiple OrderLines, the names would look and work well like this (case sensitive):

This works:

Order[0].id
Order[0].orderDate
Order[0].Customer.name
Order[0].Customer.Address
Order[0].OrderLine[0].itemID       // first order line
Order[0].OrderLine[0].description
Order[0].OrderLine[0].qty
Order[0].OrderLine[0].price

Order[0].OrderLine[1].itemID      // second order line, same names
Order[0].OrderLine[1].description
Order[0].OrderLine[1].qty
Order[0].OrderLine[1].price

However we want to add order lines and remove order lines at the client browser. Apparently, the indexes must start at zero and contain every consecutive index number to N.

The black belt ninja Phil Haack's blog entry here explains how to remove the [0] index, have duplicate names, and let MVC auto-enumerate duplicate names with the [0] notation. However, I have failed to get this to bind back using a nested object:

This fails:

Order.id                          // Duplicate names should enumerate at 0 .. N
Order.orderDate
Order.Customer.name
Order.Customer.Address
Order.OrderLine.itemID            // And likewise for nested properties?
Order.OrderLine.description
Order.OrderLine.qty
Order.OrderLine.price

Order.OrderLine.itemID
Order.OrderLine.description
Order.OrderLine.qty
Order.OrderLine.price

I haven't found any advice out there yet that describes how this works for binding back nested ViewModels on post. Any links to existing code examples or strict examples on the exact names necessary to do nested binding with ILists?

Steve Sanderson has code that does this sort of thing here, but we cannot seem to get this to bind back to nested objects. Anything not having the [0]..[n] AND being consecutive in numbering simply drops off of the return object.

Any ideas?

Answer 1

We found a work around, by using the following:

 Html.EditorFor(m => m, "ViewNameToUse", "FieldPrefix")

Where FieldPrefix is the "object[0]". This is hardly ideal, but it certainly works pretty well. It's simple and elegant.