How to place a required field validator inside a GridView TextBox

Question

I have a GridView with some TemplateField items containing TextBox controls. I would like to add a required field validator on it. This is my code:

<asp:TemplateField HeaderText="vid">
    <EditItemTemplate>
         <asp:TextBox ID="txtvid" runat="server" Width="150px"
                            Text='<%# Bind("vid") %>'>
         </asp:TextBox>
    </EditItemTemplate>
    <ItemTemplate>
         <asp:Label 
                   ID="lblvid" runat="server" 
                   Text='<%# Bind("vid") %>'>
         </asp:Label>
    </ItemTemplate>
 </asp:TemplateField>

How do I place a required field validator on txtvid?

Answer 1

In the Edit template, add a RequiredFieldValidator like this:

<EditItemTemplate>
    <asp:TextBox ID="txtvid" 
                 runat="server" Width="150px"
                 Text='<%# Bind("vid") %>'>
    </asp:TextBox>
    <asp:RequiredFieldValidator 
                 ControlToValidate="txtvid" 
                 runat="server" 
                 ErrorMessage="Please enter a 'vid' number" 
                 Text="*"/>
</EditItemTemplate>

Here is the reference for the RequiredFieldValidator on MSDN.

UPDATE:

If you wanted a regular expression validator, its pretty much the same, but with the RegularExpressionValidator control:

 <asp:RegularExpressionValidator 
     ControlToValidate="txtvid"
     ValidationExpression="\d{10}"
     runat="server" 
     ErrorMessage="Please enter a 'vid' of 10 digits" 
     Text="*"/>

Here is a complete list of the functionality for the RegularExpressionValidator on MSDN.