Gridview textbox number disappears after setting textmodenumber in edit mode

I am using html tags for most of Gridview functionality. 

I am using following html for edit, and Insert (footer)

<asp:TemplateField HeaderText="ToT Fee (In Rs)" SortExpression="ToTFeeLakh">
                <EditItemTemplate>
                    <asp:TextBox ID="txtGSTEdit" runat="server" Text='<%# Bind("ToTFeeLakh","{0:c}") %>' />
                </EditItemTemplate>
                <FooterTemplate>
                    <asp:TextBox ID="txtGSTFooter" runat="server" 
                        Text='<%# Bind("ToTFeeLakh","{0:c5}") %>' TextMode ="Number" Width ="100px" />
                </FooterTemplate>
                <ItemTemplate>
                    <asp:Label ID="Label8" runat="server" Text='<%# Bind("ToTFeeLakh", "{0:c}") %>'/>
                </ItemTemplate>
</asp:TemplateField>

 I want in edit textbox should retain its value and only interger values shall be permitted. So I am setting 

<EditItemTemplate>
                    <asp:TextBox textmode="number" ID="txtGSTEdit" runat="server" Text='<%# Bind("ToTFeeLakh","{0:c}") %>' />
                </EditItemTemplate>

but doing this make textbox value disappear in edit mode.

Pl help