当点击“编辑”按钮以后，可以看到“更新”和“取消”按钮，“取消”按钮可以正常触发RowCancelingEdit事件，但是“更新”按钮不能触发RowUpdating事件。
解决方案：
在<asp:CommandField>中添加 CausesValidation="false" 。
Gridview RowUpdating Not Firing （RowUpdating event not firing on update button click for GridView Control）
After i click edit, i will get Update and Cancel button , Cancel Works. But Update doesnt.
It’s a bug of gridview .
Solution:
Add CausesValidation="false" into <asp:CommandField> .
<asp:CommandField ShowEditButton="True" ButtonType="Button" HeaderText="Edit" CausesValidation="false">
<ItemStyle HorizontalAlign="Center" Width="140px" Font-Size="12px" BorderColor="#3D90CA"
BorderStyle="Solid" BorderWidth="1px" />
<HeaderStyle CssClass="DivReportHeader" BorderStyle="Solid" Height="20px" ForeColor="#ffffff"
BorderWidth="1px" BorderColor="#0F517E" Font-Bold="True"></HeaderStyle>
</asp:CommandField>
REF:（ http://objectmix.com/dotnet/352191-gridview-rowupdating-not-firing.html）