• enable the automatic operations for the grid
• configure from design-time the update/insert/delete parameters of the SqlDataSource controls (one for each level in the hierarchy).
• since the Select command of the data source control is fired before the Insert command (you can verify that by wiring the Inserted/Selected events for one of the SqlDataSource controls), you need to hook the InsertCommand event of the grid and define the parent key field for newly inserted detail row manually.
  
  Below is the VB.NET version of the code:
  
  

  Protected Sub RadGrid1_InsertCommand(ByVal source As Object, ByVal e As GridCommandEventArgs) Handles RadGrid1.InsertCommand

  Dim parentItem As GridDataItem = CType(e.Item.OwnerTableView.ParentItem, GridDataItem)

  nestedTableSource.InsertParameters("EmployeeID").DefaultValue = parentItem.OwnerTableView.DataKeyValues(parentItem.ItemIndex)("EmployeeID").ToString()

  End Sub

Note that you may need to modify the connection string (NorthwindConnectionString) in the web.config file of the web site to point to the Northwind SQL database. The database is present under the App_Data subfolder.

Feel free to extend the example if more nested levels need to be added.