大家来解决一个问题____________________DropDownList1 的相关....知道的就来吧
using   System;
using   System.Collections;
using   System.ComponentModel;
using   System.Data;
using   System.Drawing;
using   System.Web;
using   System.Web.SessionState;
using   System.Web.UI;
using   System.Web.UI.WebControls;
using   System.Web.UI.HtmlControls;
using   System.Data.SqlClient;
using   System.Data.OleDb;
using   System.IO;

namespace   WebApplication2
{
///   <summary>
///   WebForm1   的摘要说明。
///   </summary>
public   class   WebForm1   :   System.Web.UI.Page
{
protected   System.Web.UI.WebControls.DataGrid   DataGrid1;
protected   System.Web.UI.WebControls.TextBox   TextBox1;
protected   System.Web.UI.WebControls.Button   Button1;
SqlConnection   myCon;
protected   System.Web.UI.WebControls.DropDownList   DropDownList1;
protected   System.Web.UI.WebControls.DropDownList   DropDownList2;
int   aa;
private   void   dis()
{
myCon=new   SqlConnection(System.Configuration.ConfigurationSettings.AppSettings[ "con "]);
myCon.Open();//打开数据库
////DataGrid1数据绑定
string   sql1= "select   zhanghao_id   as   游戏帐号,zhanghao_mima   as   密码   from   table_zhanghao ";
System.Data.SqlClient.SqlDataAdapter   myDa=new   SqlDataAdapter(sql1,myCon);
DataSet   ds=new   DataSet();
myDa.Fill(ds, "table_zhanghao ");
this.DataGrid1.DataSource=ds.Tables[ "table_zhanghao "];
//this.DataGrid1.CurrentPageIndex=0;
this.DataGrid1.DataBind();
myCon.Close();
}
private   void   dis1()
{
myCon=new   SqlConnection(System.Configuration.ConfigurationSettings.AppSettings[ "con "]);
myCon.Open();//打开数据库
string   sql1= "select   zhanghao_id   from   table_zhanghao ";
System.Data.SqlClient.SqlCommand   mycom=new   SqlCommand   (sql1,myCon);
System.Data.SqlClient.SqlDataReader   mydr=mycom.ExecuteReader();
this.DropDownList1.Items.Clear();
while(mydr.Read())
{
this.DropDownList1.Items.Add(mydr.GetString(0));
}
myCon.Close();
}
private   void   Page_Load(object   sender,   System.EventArgs   e)
{
//   在此处放置用户代码以初始化页面
//if(!this.IsPostBack)
//{
dis();
dis1();

//}
}

#region   Web   窗体设计器生成的代码
override   protected   void   OnInit(EventArgs   e)
{
//
//   CODEGEN:   该调用是   ASP.NET   Web   窗体设计器所必需的。
//
InitializeComponent();
base.OnInit(e);
}

///   <summary>
///   设计器支持所需的方法   -   不要使用代码编辑器修改
///   此方法的内容。
///   </summary>
private   void   InitializeComponent()
{        
this.DataGrid1.ItemCommand   +=   new   System.Web.UI.WebControls.DataGridCommandEventHandler(this.DataGrid1_ItemCommand);
this.DataGrid1.PageIndexChanged   +=   new   System.Web.UI.WebControls.DataGridPageChangedEventHandler(this.DataGrid1_PageIndexChanged);
this.DropDownList1.SelectedIndexChanged   +=