已解决
EditItemTemplate的asp:TextBox的Text属性加入三元运算子判断null
谢谢告位^^
<asp:TemplateField HeaderText="PHONE" ItemStyle-Width="100">
<ItemTemplate>
<asp:Label ID="lblPHONE" runat="server" Text='<%#
Eval("PHONE") %>'></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="txtPHONE1" runat="server" Text='<%#
Eval("PHONE") != null ? Eval("PHONE").ToString().Trim() : ""
%>'></asp:TextBox>
</EditItemTemplate>
</asp:TemplateField>