I would recommend changing the
<asp:CommandField ShowEditButton="true" ButtonType="Button" />
to a template field and set the validationGroup to your name on the edit template fields. See below
<asp:TemplateField ShowHeader="False">
<EditItemTemplate>
<asp:LinkButton ID="lbUpdate" runat="server" CausesValidation="True"
CommandName="Update" Text="Update" ValidationGroup="EditrowValidation"></asp:LinkButton>
<asp:LinkButton ID="lbCancel" runat="server" CausesValidation="False"
CommandName="Cancel" Text="Cancel"></asp:LinkButton>
</EditItemTemplate>
<ItemTemplate>
<asp:LinkButton ID="lbEdit" runat="server" CausesValidation="False"
CommandName="Edit" Text="Edit"></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>