asp.net checkboxlist绑定数据读取出来

protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
SqlConnection con = GetDBCon.GetCon();
con.Open();
SqlDataAdapter sda = new SqlDataAdapter("select * from admin", con);
DataSet ds = new DataSet();
sda.Fill(ds,"admin");
this.CheckBoxList1.DataSource = ds.Tables[0];
this.CheckBoxList1.DataTextField = "username";//绑定的字段名
this.CheckBoxList1.DataValueField = "userid";//绑定的值
this.CheckBoxList1.DataBind();
}
}

protected void CheckBoxList1_SelectedIndexChanged(object sender, EventArgs e)
{
this.Lab2.Text = "";
for (int i = 0; i < CheckBoxList1.Items.Count; i++)
{
if (this.CheckBoxList1.Items[i].Selected)
{
this.Lab2.Text = this.Lab2.Text+CheckBoxList1.Items[i].Text+".";
}
}
}