C # Loading database data in a ComboBox control in a window

First, form one loads, binds provinces and city data

//Window Load Events        Private voidRegister_load (Objectsender, EventArgs e) {Bindpro ();//binding Province Data functions                 }        /// <summary>        ///binding Province Data functions/// </summary>         Public voidBindpro () {//Get Database Datalist<provincedata> list =NewProvinceda ().            Select (); //Add to Window            if(List! =NULL)            {                foreach(Provincedata datainchlist) {COMBOPRO.ITEMS.ADD (data.                Proname); } Combopro.selecteditem= combopro.items[0]; }        }         Public voidbindcity () {comboCity.Items.Clear (); //get the province number according to the selected province            stringProname=comboPro.SelectedItem.ToString (); stringProcode =NewProvinceda (). Selectbyproname (Proname).            Procode; //City data is bound according to the selected province numberList<citydata>list =NewCityda ().            Selectbyprocode (Procode); if(List! =NULL)            {                foreach(Citydata datainchlist) {COMBOCITY.ITEMS.ADD (data.                CityName); } Combocity.selecteditem= combocity.items[0]; }        }

Add a "content change" trigger event to the ComboBox control

Double-click, append Delegate

// Change the city        according to the selected province Private void combobox1_selectedindexchanged (object  sender, EventArgs e)        {            bindcity ();        }

Run results

C # Loading database data in a ComboBox control in a window