如何在DataGridTemplate中为每个Combobox更改/预填充SelectedIndex？

I currently have a DataGrid that has 2 columns, one of which is a DataGridTextColumn that will display items in an ObservableCollection of strings, and the second one being a DataGridTemplateColumn that holds the DataGridCellTemplate which contains the DataTemplate that displays the Combobox. The combobox also binds to an ObservableCollection of strings. Everything binds and displays as it should. I currently have a DataGrid that has 2 columns,