Commented Unassigned: ValidatorCalloutExtender [28015]

I'm in visual studio 2013 and the validatorcalloutextender is not firing. The other ajax items seem to be working such as the calendar extender.

Example:

<asp:DropDownList ID="ddlEmployee" runat="server" TabIndex="1" ToolTip="Employee who completed note." AppendDataBoundItems="true" DataSourceID="SqlDataSource1" DataTextField="Employee" DataValueField="Record_ID">
<asp:ListItem Selected="True" Text="--Select One--" Value="0" />
</asp:DropDownList>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:cn %>" SelectCommand="stpEmployee_Select_All" SelectCommandType="StoredProcedure"></asp:SqlDataSource>
<asp:RequiredFieldValidator ID="rfvEmployee" runat="server" ControlToValidate="ddlEmployee" ErrorMessage="Please select an employee who completed the note!" Font-Bold="True" ForeColor="#CC0000" InitialValue="0">*</asp:RequiredFieldValidator>
<asp:ValidatorCalloutExtender ID="vceEmployee" runat="server" TargetControlID="rfvEmployee" />

I have the latest version of Ajax 15.1.4
Comments: .NET Framework 4.5 uses [unobtrusive validation](http://www.codeproject.com/Articles/287278/Unobtrusive-Validation-with-ASP-NET) in ASP.NET by default. ValidatorCalloutExtender relies on .NET 4.0 validation, so simply upgrading the project's .NET version breaks the extender. To make it work, you need to disable unobtrusive validation by setting UnobtrusiveValidationMode to None.