从Gridview中的BoundField获取值

Question

我试图在代码隐藏中获取BoundField的值以更新到SQL服务器，但它不断给我旧的值。

HTML：

<asp:GridView ID="gridviewtxSLds" ClientIDMode="Static" runat="server" NullDisplayText="" DataKeyNames="item,AD,BD" CssClass="gridclassscrolledtx" CellPadding="0" ForeColor="#333333" OnRowCreated="gridviewtxSLds_RowCreated" AutoGenerateColumns="False">
    <Columns>
        <asp:BoundField DataField="item" ReadOnly="false" ItemStyle-CssClass="m2" HeaderText="Metric" />
        <asp:BoundField DataField="AD" ReadOnly="false" ItemStyle-CssClass="txttime" HeaderText="AD" />
        <asp:BoundField DataField="BD" ReadOnly="false" ItemStyle-CssClass="txttime" HeaderText="BD" />
    </Columns>
</asp:GridView>

点击定时按钮会触发以下功能：

 protected void Bulk_Insert(object sender, EventArgs e)
{
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < gridviewtxSLds.Rows.Count; i++)
    {
        #region textbox declarations
        string txtitem = gridviewtxSLds.DataKeys[i].Values["item"].ToString();
        string txtAD = gridviewtxSLds.DataKeys[i].Values["AD"].ToString();
        string txtBD = gridviewtxSLds.DataKeys[i].Values["BD"].ToString();
        #endregion

        #region command string
        string s = "update D" + timeinitid + "tx set AD";
        s += "='";
        s += txtAD.Trim();
        s += "', ";
        s += "BD";
        s += "='";
        s += txtBD.Trim();
        s += "' where item";
        s += "='";
        s += txtitem.Trim();
        s += "';";
        #endregion
        sb.Append(s.ToString());
    }
    SqlCommand cmd = new SqlCommand(sb.ToString(), con);
    con.Open();
    cmd.ExecuteNonQuery();
}

如果我更改gridview中的值，它仍会将旧值发送到数据库。知道为什么吗？