Updating inserted data in table based on datatable

 public DataTable update_files()
    {
        SqlConnection con = new SqlConnection("s");
        con.Open();
        SqlCommand cmd;
        cmd = new SqlCommand("update [order] set sum=@sum where order_id=@order_id", con);
        cmd.Parameters.AddWithValue("@sum", sp);
        cmd.Parameters.AddWithValue("@order_id", sp1);
        DataTable dt = new DataTable();
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        da.Fill(dt);
        con.Close();
        return dt;
    }

 
protected void Button1_Click(object sender, EventArgs e)
    {
        DataTable dt = new DataTable();
        DataTable dt1 = new DataTable();

        DataColumn dc=new DataColumn("sum");
        DataColumn dc1=new DataColumn("id");
        dt.Columns.Add(dc);
        dt.Columns.Add(dc1);

        DataRow dr=dt.NewRow();
        dr["sum"]=TextBox3.Text;
        dr["id"]=TextBox4.Text;
        dt.Rows.Add(dr);

       foreach(DataRow drow in dt.Rows)
       {
           sp = drow["sum"].ToString();
           sp1 = Convert.ToInt16(drow["id"]);
           dt1 = update_files();
       }

    }