选择组合框时的默认文本

Question

I have two combo boxes, ComboBox Country and ComboBox City. When I change value in ComboBox Country, ComboBox City will be filled with Cities from Country I choose in first combobox. Is it possible every time i change ComboBox Country value, the combobox City show "Please Choose City"?. Because in my current condition, ComboBox City will show the cities from country i choose (eg London, Manchester). Here is my current code to fill ComboBox City

  dtTable = SQLqueryGetListCities
  ComboBoxCity.DataSource = dtTable

Answer 1

dtTable = SQLqueryGetListCities

DataRow dr = dtTable.NewRow();
dr["CityID"] = "0";
dr["CityName"] = "Select City";
dtTable.Rows.InsertAt(dr, 0);
dtTable.AcceptChanges();

ComboBoxCity.DataSource = dtTable