怎么在asp.net项目中实现一个批量删除功能

<asp:GridView ID="GridView1" runat="server" Width="100%" EmptyDataText="暂时无数据" BorderColor="White" OnRowDeleting="GridView1_RowDeleting">
<Columns>
<asp:TemplateField HeaderText="选择">
<ItemStyle Width="20px" />
    <ItemTemplate>
      <asp:CheckBox id="id" runat="Server" />
    </ItemTemplate>
  </asp:TemplateField>
   <asp:BoundField DataField="id" HeaderText="序号" >
 <ItemStyle Width="20px" />
   </asp:BoundField>
   <asp:TemplateField HeaderText="标题">
 <ItemStyle Width="400px" />
 <ItemTemplate>
   <a href="../shangpu/<%#eval_r("pageurl") %>" target="_blank"><%#eval_r("title") %></a>
 </ItemTemplate>
   </asp:TemplateField>
   <asp:TemplateField HeaderText="发表时间">
 <ItemStyle Width="100px" />
 <ItemTemplate>
   <%# Convert.ToDateTime(eval_r("addtime")).Date.ToString("yyyy-MM-dd") %>
 </ItemTemplate>
   </asp:TemplateField>
   <asp:HyperLinkField DataNavigateUrlFormatString="shangpu_edit.aspx&#63;id={0}" Text="修改" NavigateUrl="shangpu_edit.aspx&#63;id={0}" DataNavigateUrlFields="id" >
 <ItemStyle Width="30px" />
   </asp:HyperLinkField>
    <asp:CommandField ShowDeleteButton="True" HeaderText="删除" DeleteText="<div id="de" onclick="JavaScript:return confirm('确定删除吗？')">删除</div>" >
 <ItemStyle Width="30px" />
   </asp:CommandField>
 </Columns>
 <EmptyDataTemplate>
 <font color=red>暂时无数据</font>
 </EmptyDataTemplate>
<RowStyle Height="20px" />
  </asp:GridView> 

protected void btndeleteall_Click(object sender, EventArgs e)
{
string sqltext = "(";
for (int i = 0; i < GridView1.Rows.Count; i++)
{
  CheckBox chb = (CheckBox)GridView1.Rows[i].FindControl("id");
  if (chb.Checked)
  {
 sqltext = sqltext + GridView1.DataKeys[i].Value.ToString() + ",";
  }
}
sqltext = sqltext.Substring(0, sqltext.Length - 1) + ")";
sqltext = "delete from shangpu where id in" + sqltext;
string sqlcon = ConfigurationManager.AppSettings["ConnectionString"].ToString();
SqlConnection con = new SqlConnection(sqlcon);
con.Open();
SqlCommand cmd = new SqlCommand(sqltext, con);
try
{
  int count = Convert.ToInt32(cmd.ExecuteNonQuery());
  if (count > 0)
  {
 viewbind();
 MessageBox.Show(this, "删除成功,共删除" + count + "条记录！");
  }
}
catch
{
  MessageBox.Show(this, "删除失败！");
}
finally
{
  con.Close();
  con.Dispose();
}
}