Hi there... still new so please forgive me if I make a mistake... to add validation to a textbox that is inside a gridview...
1. Convert the field into a text field...
2. then add validation into the <EditItemTemplate></EditItemTemplate> and the <InsertItemTemplate></InsertItemTemplate>
as below... :
<asp:TemplateField HeaderText="Client Number" SortExpression="ClientNumber">
<EditItemTemplate>
<asp:TextBox ID="txtClientNumber" runat="server" Text='<%# Bind("ClientNumber") %>'></asp:TextBox>
</EditItemTemplate>
<InsertItemTemplate>
<asp:TextBox ID="txtClientNumber" runat="server" Text='<%# Bind("ClientNumber") %>'></asp:TextBox>
<asp:RequiredFieldValidator ID="val1" runat="server" ControlToValidate="txtClientNumber" ErrorMessage="Client Number Required" Display="Dynamic"></asp:RequiredFieldValidator>
</InsertItemTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("ClientNumber") %>'></asp:Label>
</ItemTemplate>
<ControlStyle CssClass="editControlTextFields" Width="96%" />
<HeaderStyle Width="110px" />
</asp:TemplateField>