send the current value of Combo Box into the DataBase

i want to insert the value of ComboBox into the DataBase but i don't know the related Code with this Event of ComboBox "SelectedValueChanged"i use a database for initializing combobox, For example fill it with "database a" , i use BindingSource to add this DataBase in ComboBoxi want when i choose any item of ComboBox,add that item in the other DataBase For example"database b",i can't update DataBase b with value of ComboBox