問題：

在GridView中，在使用者點選按鈕的事件中可以使用下面的方法取當前行中某一列的值(從幫助裡copy出來的程式碼)

int index = Convert.ToInt32(e.CommandArgument);
// Retrieve the row that contains the button clicked 
// by the user from the Rows collection.
GridViewRow row = CustomersGridView.Rows[index];
            
item.Text = Server.HtmlDecode(row.Cells[2].Text);

問題來了，如果你把一列設為隱藏，就發現取出來的是空值。

解決方案：

1 在GridView中將主鍵EmployeeID這一列設為隱藏Visible ="false" ， 增加一個button列。同時要注意，將GridView的DataKeyNames設定為"EmployeeID" 

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"   DataKeyNames="EmployeeID"  DataSourceID="SqlDataSource1" OnRowCommand="GridView1_RowCommand"        >
        <Columns>
            <asp:BoundField DataField="EmployeeID" HeaderText="EmployeeID" ReadOnly="True" SortExpression="EmployeeID"  Visible ="false" />
            <asp:BoundField DataField="Title" HeaderText="Title" SortExpression="Title" />
            <asp:BoundField DataField="LastName" HeaderText="LastName" SortExpression="LastName" />
            <asp:BoundField DataField="FirstName" HeaderText="FirstName" SortExpression="FirstName" />
            <asp:BoundField DataField="WorkPhone" HeaderText="Phone" SortExpression="WorkPhone" />
            <asp:BoundField DataField="MobilePhone" HeaderText="Mobile" SortExpression="MobilePhone" />
            <asp:ButtonField HeaderText = "Detail" ButtonType="Button" Text ="Detail" CommandName="Detail"    />  
        </Columns>
    </asp:GridView>

2 在GridView1_RowCommand事件中取得EmployeeID列的值

   protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "Detail")
        {

            // Convert the row index stored in the CommandArgument
            // property to an Integer.
            int index = Convert.ToInt32(e.CommandArgument);

            // Get the Key value from the GridView control.
            DataKey key = GridView1.DataKeys[index ];

            string employeeid = key.Value.ToString() ;

            Session["EmployeeID"] = employeeid;
            Server.Transfer("EditEmployee.aspx");

        }

這裡，要點是GridView使用了DataKeys來儲存關鍵列的資料，而不是以前ASP1.1中的那種方式了。如果要把列加入DataKeys，需要在GridView的DataKeyNames屬性中加入列名，而且支援多個列，中間用逗號分割。不僅GridView有此特性，DetailView和FormView都有這樣的屬性。