>I have "moved" (copied) my VS 2005 project (.NET 2.0) to VS 2012. Now (in VS 2012) under .NET 4.0 the validation does not work. Strange is that I created a test aspx page with the same validation as in one of the application pages; and the validation works in the test page. But not in one of the pages of the application. So there must be something different.
>
>How do you troubleshoot the validation? Where in the debugger (if this is where I should look) I can see the validation?
>
>This is the segment of code of my validation:
>

>  <asp:textbox id="RequestorPhone" CssClass="FieldRW" MaxLength="14" Runat="server"></asp:textbox>
>			<asp:requiredfieldvalidator id="rfvRequestorPhone" runat="server" CssClass="FieldLabel" ControlToValidate="RequestorPhone"
>			ErrorMessage="RequiredFieldValidator" Enabled="True">  Please enter your telephone</asp:requiredfieldvalidator>  
>        <asp:button id="Submit" Runat="server" Text="Submit" ></asp:button>  
>

Do you mean you don't see errors when you press Submit button? The above looks like server side validation, does the test page show errors right away (client side validation)?