源错误: 
行 20:         SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["sjk"]);
行 21:         SqlDataAdapter sda = new SqlDataAdapter();
行 22:         con.Open();
行 23:         sda.SelectCommand = new SqlCommand("select name from tezheng", con);
行 24:         DataSet ds = new DataSet();
 
文件源码:
        SqlConnection con = new SqlConnection(ConfigurationManager.AppSettings["sjk"]);
        SqlDataAdapter sda = new SqlDataAdapter();
        con.Open();
        sda.SelectCommand = new SqlCommand("select name from tezheng", con);
        DataSet ds = new DataSet();
        sda.Fill(ds, "tz");
        this.DropDownList1.DataSource = ds.Tables["tz"];
        this.DropDownList1.DataTextField = "name";
        this.DropDownList1.DataValueField = "id";
        this.DropDownList1.DataBind();        con.Close();