How to validate field inside a gridview and show errors in message box.

<asp:GridView ID="GridView1" runat="server" AllowPaging="True" AutoGenerateColumns="False"
                                                                          CssClass="GridStyle"
                                                                            Font-Names="Tahoma" Font-Size="11px"
                                                                            HeaderStyle-CssClass="HeaderStyle" HorizontalAlign="Left"

                                                                             Width="100%">
                                                                            <%--<RowStyle BorderColor="Silver" BorderStyle="Solid" BorderWidth="1px" ForeColor="Blue"
                                                    Wrap="True" />--%>
                                                                            <Columns>

                                                                                     <asp:CommandField
               ShowEditButton="True" CausesValidation="true" ValidationGroup="ValGrpEdit"></asp:CommandField>


                                                                                <asp:TemplateField ShowHeader="False">
                                                                                    <ItemTemplate>
                                                                                        <asp:LinkButton ID="lnkDelete" runat="server" CausesValidation="False"
                                                                                            CommandName="Delete" Text="Delete"></asp:LinkButton>
                                                                                    </ItemTemplate>
                                                                                </asp:TemplateField>

                                                                                <asp:TemplateField HeaderText="Name" SortExpression="Name">
                                                                                    <EditItemTemplate>
                                                                                        <asp:TextBox ID="Name1" runat="server" CssClass="text" Text='<%# Bind("Name") %>'
                                                                                            ValidationGroup="ValGrpEdit"></asp:TextBox>
                                                                                        <asp:RequiredFieldValidator ID="RequiredName" runat="server" ControlToValidate="Name1"
                                                                                            ErrorMessage="Please enter a valid Name."  EnableClientScript="true" ValidationGroup="ValGrpEdit" Width="16px">*</asp:RequiredFieldValidator>
                                                                                    </EditItemTemplate>
                                                                                    <ItemTemplate>
                                                                                        <asp:Label ID="Name2" runat="server" Text='<%# Bind("Name") %>'></asp:Label>
                                                                                    </ItemTemplate>
                                                                                    <ItemStyle ForeColor="Black" Width="15%" />
                                                                                    <ControlStyle />
                                                                                </asp:TemplateField>




                                                                                <asp:TemplateField HeaderText="Path" SortExpression="Path">
                                                                                    <EditItemTemplate>
                                                                                        <asp:TextBox ID="Path1"  ValidationGroup="ValGrpEdit" runat="server" CssClass="text" Height="76px" Text='<%# Bind("Path") %>'
                                                                                            TextMode="MultiLine"></asp:TextBox>
                                                                                        <asp:CustomValidator ID="txtApplicationPathV" ValidationGroup="ValGrpEdit" runat="server"
                                                                                            ErrorMessage="Please fill in a path either in URL / Path or URL / Path" ClientValidationFunction="ValidateEdit"
                                                                                            ControlToValidate="Path1" ValidateEmptyText="true">*</asp:CustomValidator>
                                                                                    </EditItemTemplate>
                                                                                    <ItemTemplate>
                                                                                        <asp:Label ID="Path2" runat="server" CssClass="DisplayDesc" Text='<%# Bind("Path") %>'
                                                                                            Visible="false"></asp:Label>

                                                                                    </ItemTemplate>
                                                                                    <ItemStyle ForeColor="Black" />
                                                                                    <ControlStyle />
                                                                                </asp:TemplateField>




                                                                            </Columns>

                                                                        </asp:GridView>