第一种解决方法（本人成功）：在后台页
int num = int.Parse(gv.DataKeys[dr.RowIndex].Values[0].ToString());
第二种解决方法：（摘自 http://www.cnblogs.com/Jinglecat/archive/2007/09/12/813338.html）
在 GridView/DetailsView 中如果 BoundField 的 Visible=false 时, 回发的时候无法此列的值（GridViewRow.Cells[cellIndex].Text将为空)，网上很多朋友提出了各种各样的解决方案，这里整理一下，并提供示例。
未反射 GridView 类，不曾仔细阅读其源码，不知内部实现对于 BoundField（普通绑定列），当此列 Visible=false 时，是未执行绑定计算，还是未保持 ViewState，也许这是就是传说的GridView性能由于DataGrid的一点吧。事实上，这样反而给粗心的开发者带来了“莫名其妙”的问题。DataGrid 中 BoundColumn 不存在此问题。
MSDN 对此是这样的说明：
备注使用 Visible 属性显示或隐藏数据绑定控件中的 DataControlField 对象。如果 Visible 属性为 false，则不显示数据值并且不做到客户端的往返行程。如果要往返不可见字段的数据，请将字段名添加到数据绑定控件的 DataKeyNames 属性。http://msdn2.microsoft.com/zh-cn/library/system.web.ui.webcontrols.datacontrolfield.visible(VS.80).aspx
说明：BoundField 类继承自 DataControlField 类。
事实上，实际项目中，我几乎没有使用隐藏列的经验，即使在 1.x 的 DataGrid 中，为了记录某些有用的隐藏信息，我一般使用模板列中嵌套控件，如label 并设置其visible=false 最佳当然是用 input type=hidden runat=server（注：1.x 中没有 asp:hiddenfield 控件)。
而 2.0 ，最佳的方案，当然是使用 DataKeys 来存储，不像DataGrid.DataKey ，GridView/DetailsView.DataKeys 可以存储多个值。
以下为示例代码，代码包含各种方案的“自说明”注释，不再做过多的解释。
代码
<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<%--http://community.csdn.net/Expert/TopicView3.asp?id=5646507--%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack) {
LoadProductData();
}
}
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
// 客户端 CSS 控制隐藏，不安全，毕竟数据还是呈现到客户端了
e.Row.Cells[3].Style.Add(HtmlTextWriterStyle.Display, "none");
// 设置单元格隐藏, TableCell.Visible=false, OK
e.Row.Cells[4].Visible = false;
}
protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
int rowIndex = -1;
switch (e.CommandName) {
case "Select":
rowIndex = Convert.ToInt32(e.CommandArgument);
GridViewRow row = GridView1.Rows[rowIndex];
Response.Write(String.Format("<pre style='color:red'>您选择了第 {0} 行\n当前行 ProductId={1}, CategoryId={2}（两者均由DataKeys获取）\n",
(row.RowIndex + 1),
GridView1.DataKeys[rowIndex].Values["ProductId"],
GridView1.DataKeys[rowIndex].Values["CategoryId"]));
for (int columnIndex=0; columnIndex< GridView1.Columns.Count; columnIndex++) {
DataControlField field = GridView1.Columns[columnIndex];
string text = null;
if (field is BoundField) {
text = row.Cells[columnIndex].Text;
}
else if (field is TemplateField) {
Label lbl = row.Cells[columnIndex].FindControl("lblProductID") as Label;
if (lbl != null) {
text = lbl.Text;
}
else {
text = row.Cells[columnIndex].Text;
}
}
Response.Write(String.Format("{0}#Type={1}#Visible={2}#CanGetText={3}#Text={4}\n",
field.HeaderText, field.GetType().Name.ToString(), field.Visible, !String.IsNullOrEmpty(text), text));
}
Response.Write("</pre>");
break;
}
}
void LoadProductData()
{
DataTable dt = CreateProductTable();
GridView1.DataSource = dt;
GridView1.DataBind();
}
#region sample data
static DataTable CreateProductTable()
{
DataTable tbl = new DataTable("Products");
tbl.Columns.Add("ProductID", typeof(int));
tbl.Columns.Add("ProductName", typeof(string));
tbl.Columns.Add("CategoryID", typeof(int));
DataRow row = tbl.NewRow();
row[0] = 1;
row[1] = "Chai";
row[2] = 1;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 2;
row[1] = "Chang";
row[2] = 1;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 3;
row[1] = "Aniseed Syrup";
row[2] = 2;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 4;
row[1] = "Chef Anton's Cajun Seasoning";
row[2] = 2;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 5;
row[1] = "Chef Anton's Gumbo Mix";
row[2] = 2;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 47;
row[1] = "Zaanse koeken";
row[2] = 3;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 48;
row[1] = "Chocolade";
row[2] = 3;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 49;
row[1] = "Maxilaku";
row[2] = 3;
tbl.Rows.Add(row);
return tbl;
}
#endregion
protected void Button1_Click(object sender, EventArgs e)
{
LoadProductData();
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Demo6_AccessHiddenGridViewColumnValue</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:GridView ID="GridView1" DataKeyNames="ProductId,CategoryId" runat="server" AutoGenerateColumns="False" OnRowCommand="GridView1_RowCommand" OnRowDataBound="GridView1_RowDataBound" CellPadding="4" ForeColor="#333333">
<Columns>
<asp:BoundField DataField="ProductID" HeaderText="列0 正常状态"/>
<asp:BoundField DataField="ProductID" HeaderText="列1 直接设置Visible=false 无法获取值" Visible="False" />
<asp:BoundField DataField="ProductID" HeaderText="列2 width=0 客户端依然呈现无效">
<ItemStyle Width="0px" />
</asp:BoundField>
<asp:BoundField DataField="ProductID" HeaderText="列3 客户端 CSS 控制隐藏，不安全，毕竟数据还是呈现到客户端了"/>
<asp:BoundField DataField="ProductID" HeaderText="列4 设置单元格隐藏, TableCell.Visible=false, OK"/>
<asp:TemplateField HeaderText="列5 模板列直接调用 Eval " Visible="False">
<ItemTemplate>
<%# Eval("ProductID") %>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="列6 模板列嵌入 Label" Visible="False">
<ItemTemplate>
<asp:label ID="lblProductID" runat="server" Text='<%# Eval("ProductID") %>' />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="ProductName" HeaderText="列7"/>
<asp:ButtonField CommandName="Select" Text="Select" HeaderText="列8 按钮" />
</Columns>
<FooterStyle BackColor="#990000" Font-Bold="True" ForeColor="White" />
<RowStyle BackColor="#FFFBD6" ForeColor="#333333" />
<SelectedRowStyle BackColor="#FFCC66" Font-Bold="True" ForeColor="Navy" />
<PagerStyle BackColor="#FFCC66" ForeColor="#333333" HorizontalAlign="Center" />
<HeaderStyle BackColor="#990000" Font-Bold="True" ForeColor="White" />
<AlternatingRowStyle BackColor="White" />
</asp:GridView></div>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="重新绑定数据" />
</form>
</body>
</html>
<%@ Import Namespace="System.Data" %>
<%--http://community.csdn.net/Expert/TopicView3.asp?id=5646507--%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack) {
LoadProductData();
}
}
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
// 客户端 CSS 控制隐藏，不安全，毕竟数据还是呈现到客户端了
e.Row.Cells[3].Style.Add(HtmlTextWriterStyle.Display, "none");
// 设置单元格隐藏, TableCell.Visible=false, OK
e.Row.Cells[4].Visible = false;
}
protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
int rowIndex = -1;
switch (e.CommandName) {
case "Select":
rowIndex = Convert.ToInt32(e.CommandArgument);
GridViewRow row = GridView1.Rows[rowIndex];
Response.Write(String.Format("<pre style='color:red'>您选择了第 {0} 行\n当前行 ProductId={1}, CategoryId={2}（两者均由DataKeys获取）\n",
(row.RowIndex + 1),
GridView1.DataKeys[rowIndex].Values["ProductId"],
GridView1.DataKeys[rowIndex].Values["CategoryId"]));
for (int columnIndex=0; columnIndex< GridView1.Columns.Count; columnIndex++) {
DataControlField field = GridView1.Columns[columnIndex];
string text = null;
if (field is BoundField) {
text = row.Cells[columnIndex].Text;
}
else if (field is TemplateField) {
Label lbl = row.Cells[columnIndex].FindControl("lblProductID") as Label;
if (lbl != null) {
text = lbl.Text;
}
else {
text = row.Cells[columnIndex].Text;
}
}
Response.Write(String.Format("{0}#Type={1}#Visible={2}#CanGetText={3}#Text={4}\n",
field.HeaderText, field.GetType().Name.ToString(), field.Visible, !String.IsNullOrEmpty(text), text));
}
Response.Write("</pre>");
break;
}
}
void LoadProductData()
{
DataTable dt = CreateProductTable();
GridView1.DataSource = dt;
GridView1.DataBind();
}
#region sample data
static DataTable CreateProductTable()
{
DataTable tbl = new DataTable("Products");
tbl.Columns.Add("ProductID", typeof(int));
tbl.Columns.Add("ProductName", typeof(string));
tbl.Columns.Add("CategoryID", typeof(int));
DataRow row = tbl.NewRow();
row[0] = 1;
row[1] = "Chai";
row[2] = 1;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 2;
row[1] = "Chang";
row[2] = 1;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 3;
row[1] = "Aniseed Syrup";
row[2] = 2;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 4;
row[1] = "Chef Anton's Cajun Seasoning";
row[2] = 2;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 5;
row[1] = "Chef Anton's Gumbo Mix";
row[2] = 2;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 47;
row[1] = "Zaanse koeken";
row[2] = 3;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 48;
row[1] = "Chocolade";
row[2] = 3;
tbl.Rows.Add(row);
row = tbl.NewRow();
row[0] = 49;
row[1] = "Maxilaku";
row[2] = 3;
tbl.Rows.Add(row);
return tbl;
}
#endregion
protected void Button1_Click(object sender, EventArgs e)
{
LoadProductData();
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Demo6_AccessHiddenGridViewColumnValue</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:GridView ID="GridView1" DataKeyNames="ProductId,CategoryId" runat="server" AutoGenerateColumns="False" OnRowCommand="GridView1_RowCommand" OnRowDataBound="GridView1_RowDataBound" CellPadding="4" ForeColor="#333333">
<Columns>
<asp:BoundField DataField="ProductID" HeaderText="列0 正常状态"/>
<asp:BoundField DataField="ProductID" HeaderText="列1 直接设置Visible=false 无法获取值" Visible="False" />
<asp:BoundField DataField="ProductID" HeaderText="列2 width=0 客户端依然呈现无效">
<ItemStyle Width="0px" />
</asp:BoundField>
<asp:BoundField DataField="ProductID" HeaderText="列3 客户端 CSS 控制隐藏，不安全，毕竟数据还是呈现到客户端了"/>
<asp:BoundField DataField="ProductID" HeaderText="列4 设置单元格隐藏, TableCell.Visible=false, OK"/>
<asp:TemplateField HeaderText="列5 模板列直接调用 Eval " Visible="False">
<ItemTemplate>
<%# Eval("ProductID") %>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="列6 模板列嵌入 Label" Visible="False">
<ItemTemplate>
<asp:label ID="lblProductID" runat="server" Text='<%# Eval("ProductID") %>' />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="ProductName" HeaderText="列7"/>
<asp:ButtonField CommandName="Select" Text="Select" HeaderText="列8 按钮" />
</Columns>
<FooterStyle BackColor="#990000" Font-Bold="True" ForeColor="White" />
<RowStyle BackColor="#FFFBD6" ForeColor="#333333" />
<SelectedRowStyle BackColor="#FFCC66" Font-Bold="True" ForeColor="Navy" />
<PagerStyle BackColor="#FFCC66" ForeColor="#333333" HorizontalAlign="Center" />
<HeaderStyle BackColor="#990000" Font-Bold="True" ForeColor="White" />
<AlternatingRowStyle BackColor="White" />
</asp:GridView></div>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="重新绑定数据" />
</form>
</body>
</html>