in easy way fist you need to make one selectionChanged event for you list box and here make your combobox and textbox isenabled proeprty as false
private void ListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
textbox1.IsEnabled = false;
combobox1.IsEnabled = false;
}
here
is user Chang value for list box that means that select any of item in list box at a time combobox and textbox will be disabled