ComboBox is not Refreshed

Hello,

I have a combobox in my one form like City name, And I have Master form for that so I defined fill city combo public so i can call it on form close event of that master...

but combobox is not refreshed with new add or delete value...

Here is my code..

string qry = "Select * from City";
        dtcity = cc.GetDataSection(qry, connection);
        cmbCity.DataSource = null;
        cmbCity.DisplayMember = "CityName";
        cmbCity.ValueMember = "CityId";
        cmbCity.DataSource = dtcity ;

I am getting perfect data in datatable but not in combo box....

Any help would be appreciate..

Thank u...