selectionchangecommitted vs selectedindexchanged

 selectionchangecommitted vs selectedindexchanged

SelectionChangeCommitted is raised only when the user changes the combo box selection. 
Do not use SelectedIndexChanged or SelectedValueChanged to capture user changes, because those events are also raised when the selection changes programmatically.

You can create a SelectionChangeCommitted event handler to provide special handling for the ComboBox when the user changes the selected item in the list.