<asp:TemplateField HeaderText="Quantity">
    <itemtemplate>
    <asp:TextBox ID="editQuantity" runat="server" CssClass="GridEditingRow"   Width="24px" MaxLength="2" Text='<%#Eval("Quantity")%>' />
    </itemtemplate>
</asp:TemplateField>

protected void updateButton_Click(object sender, EventArgs e)
{
    int rowsCount = grid.Rows.Count;
    GridViewRow gridRow;
    TextBox quantityTextBox;
    string productId;
    int quantity;
    bool success = true;
    // 遍歷GridView中的每一行
    for (int i = 0; i < rowsCount; i++)
    {
        // 獲行當前行
        gridRow = grid.Rows[i];
        // 通過DATAKEYS來取行沒顯示出來的ID號
        Id = grid.DataKeys[i].Value.ToString();
        // 
        quantityTextBox = (TextBox)gridRow.FindControl("editQuantity");
        // 轉換為整形，如果輸入的是非法字符Int32.TryParse返回FALSE
        if (Int32.TryParse(quantityTextBox.Text, out quantity))
        {
            // 調用業務層的方法更新數據
            success = success && BLL.UpdateItem(Id, quantity);
        }
        else
        {
            // 更新失敗
            success = false;
        }
        // 顯示信息
        statusLabel.Text = success ?
          "<br />更新成功！<br />" :
          "<br />更新失敗！<br />";
    }
    // 重新綁定GridVIEW
    PopulateGridView();
}