You can find attached a small web site I have created that demonstrates this. Some sample object factory is also included. Note that I have used two different ways of editing sub-objects of the main data object. In the first example, I create a template column where in the EditItemTemplate, I have editing fields bound to the sub-property of the data item. In the second case, I use an automatic data column (GridNumericColumn) with DataField="Stock.Quantity"
that automatically allows me to show the value of the sub-property in the edit form.
Back in the code-behind I use the UpdateCommand and InsertCommand events to extract the edited values straight into a data entity object (Product) and then update my data source and grid.
Check the example out and let me know if further clarification is required.
the Telerik team