private void cbxProvince_SelectedIndexChanged(object sender, EventArgs e) { AreaInfo provinceAreaInfo = this.cbxProvince.SelectedItem as AreaInfo; //判断是否 拿到的城市为空 if (provinceAreaInfo == null) { return; } //根据省的Id获取所有的城市信息 //加载数据库中的所有的省的数据 string connStr = ConfigurationManager.ConnectionStrings["sqlConn"].ConnectionString; //创建链接对象 using (SqlConnection conn = new SqlConnection(connStr)) { using (SqlCommand cmd = conn.CreateCommand()) { conn.Open();//***********8 cmd.CommandText = @"select AreaId, AreaName, AreaPid from [dbo].[AreaFull] where AreaPId=" + provinceAreaInfo.AreaId; using (SqlDataReader reader = cmd.ExecuteReader()) { this.cbxCity.Items.Clear(); while (reader.Read()) { //int AreadId = int.Parse(reader["AreaId"].ToString()); //把表格的数据转换成 对象数据 AreaInfo areaInfo = new AreaInfo(); areaInfo.AreaId = int.Parse(reader["AreaId"].ToString()); areaInfo.AreaName = reader["AreaName"].ToString(); areaInfo.AreaPId = int.Parse(reader["AreaPId"].ToString()); //把省的信息放到 ComboBox中。ComboBox显示信息是 Item对象的ToString() this.cbxCity.Items.Add(areaInfo); } } //end useing reader } //end useing cmd } //en this.cbxCity.SelectedIndex = 0; }