WPF: How to set the SelectedValue on Data Bound ComboBox

Most of the time when you have a form, you will have some combo boxes, and some list boxes. If you are editing an existing item, most likely you are going to want to have these items display the currently selected value. So we are going to populate a form with some contacts and provide a combo box of companies that they could work for. When we select an individual contact from our list, we would expect the combo box to change and show the company the contact currently is associated with.