how to refresh a combobox in c#

Question

how to refresh a combobox when child form closed,

Without refresh windows form in windows application.....??

 

 

In my c# application there is a combo box listing 'customer names' which is placed in the MainForm .There is a button for adding new customers when clicking on the button another form opens and we need to save customer details. After this i want to reload the 'MainForm' for the combobox to include the new name or the combobox to display the new name .