在wpf中，即使选择没有改变，如何确保我获得组合框的选定索引

I am developing a module where i want to know which item is selected by user in combobox, I am using SelectionChanged event of ComboBox but it doesn't fire if i don't change selection to another item in list, so in short which event i should use so as to get current selection of user though he may or may not change the selectionI am developing a module where i want to know w