C # XML Provincial linkage

Using system;using system.collections.generic;using system.componentmodel;using system.data;using System.Drawing; Using system.linq;using system.text;using system.windows.forms;using system.xml;using System.IO;namespace windowsformsapplication1{public partial class Form1:form {public Form1 () {Initializeco        Mponent ();        } list<string> Sheng = new list<string> ();        list<string> shi = new list<string> ();        list<string> qua = new list<string> ();            private void Form1_Load (object sender, EventArgs e) {XmlDocument doc = new XmlDocument (); Doc.            Load ("Provinces.xml");            ComboBox1.Items.Clear (); Sheng.            Clear (); XmlNodeList nodelist = doc.                     SelectNodes ("/provinces/province"); foreach (XmlNode item in nodelist) {COMBOBOX1.ITEMS.ADD (item. attributes["Provincename"].                Value); Sheng. ADD (item.attributes["ID"].                            Value);                   } combobox1.selectedindex = 0; private void ComboBox1_SelectedIndexChanged (object sender, EventArgs e) {XmlDocument XM = new            XmlDocument (); Xm.            Load ("Cities.xml"); Shi.            Clear ();            ComboBox2.Items.Clear ();            String cid = Sheng[combobox1.selectedindex]; XmlNodeList Citys = xm.                        SelectNodes ("/cities/city[@PID =" +cid+ "]"); foreach (XmlNode item in citys) {COMBOBOX2.ITEMS.ADD (item. attributes["CityName"].                    Value); Shi. ADD (item. attributes["ID"].                            Value);        } combobox2.selectedindex = 0; private void Combobox3_selectedindexchanged (object sender, EventArgs e) {} Priva te void Combobox2_selectedindexchanged (object sender, EventArgs e) {XmlDocument qu = new XMLDOcument (); Qu.            Load ("Districts.xml"); Qua.            Clear ();            ComboBox3.Items.Clear ();            String qid = shi[combobox2.selectedindex]; XmlNodeList Qux = qu.            SelectNodes ("/districts/district[@CID =" + qid + "]"); foreach (XmlNode item in Qux) {COMBOBOX3.ITEMS.ADD (item. attributes["Districtname"].                Value); Qua. ADD (item. attributes["ID"].            Value);        } combobox3.selectedindex = 0; }    }}

　　

C # XML Provincial linkage