C#通讯录管理系统新增，修改，查询···

C#通讯录管理系统新增，修改，查询···
usingSystem;usingSystem.Collections.Generic;usingSystem.ComponentModel;usingSystem.Data;usingSystem.Drawing;usingSystem.Text;usingSystem.Windows.Forms;usingSystem.Data.SqlClient;usingSystem.Configuration;namespacePhoneBook{publicpartialclassfrmMain:Form{publicfrmMain(){InitializeComponent();}privatestringstrConn=System.Configuration.ConfigurationManager.AppSettings["ConnectionString"];privatevoidfrmMain_Load(objectsender,EventArgse){LoadGroup();if(trvGroup.Nodes.Count＞0){trvGroup.SelectedNode=trvGroup.Nodes[0];LoadList();}else{lvContact.Clear();}}privatevoidLoadGroup(){try{trvGroup.Nodes.Clear();SqlConnectionconn=newSqlConnection(strConn);SqlCommandcmd=newSqlCommand();cmd.Connection=conn;cmd.CommandText="selectdistinct组别from联系人where用户名='"+tsslUserName.Text+"'";conn.Open();SqlDataReadersdr=cmd.ExecuteReader();while(sdr.Read()){trvGroup.Nodes.Add(sdr[0].ToString());}sdr.Close();conn.Close();}catch{}}privatevoidLoadList(){if(trvGroup.Nodes.Count==0){lvContact.Clear();return;}if(trvGroup.SelectedNode.Index＞=0){stringstrGroup=trvGroup.SelectedNode.Text;try{lvContact.Clear();lvContact.Columns.Add("姓名",100);lvContact.Columns.Add("工作