To be completed in C# using WPF form -- create update def table form

The last form needed is a form to update the def table which contains all the items for the business. This form can be accessed through the menu and only when an invoice is not being edited or a new invoice is being entered. This form will list all the items in a list (like a DataGrid). The items will consist of a name, cost, and description. From here the user can add new items, edit existing items, or delete existing items. If the user tries to delete an item that is on an invoice, dont allow the user to do so. Instead warn them with a message that tells the user which invoices that item is used on. When the user closes the update def table form, make sure to update the drop down box as to reflect any changes made by the user. Also update the current invoice because its item name might have been updated.