I have a very simple ASPX page and followed the installation procedures for Telerik UI for ASP.NET AJAX, all seems good and no errors when entering the source ... but as soon as I hit "Design" tab in VS 2015 IDE to view I get the following error for any Telerik control reference:
<%@ Page Language="vb" AutoEventWireup="false" CodeBehind="Login.aspx.vb" Inherits="DC.Web.Login" %>
<%@ Register Assembly="Telerik.Web.UI" Namespace="Telerik.Web.UI" TagPrefix="telerik" %>
<!DOCTYPE html>
<
html
xmlns
=
"http://www.w3.org/1999/xhtml"
>
<
head
runat
=
"server"
>
<
title
>Login</
title
>
</
head
>
<
body
>
<
form
id
=
"Login"
runat
=
"server"
>
<!-- RadScriptManager is required for all AJAX based controls -->
<
telerik:RadScriptManager
ID
=
"rsmLogin"
runat
=
"server"
></
telerik:RadScriptManager
>
<
telerik:RadSkinManager
ID
=
"rskmLogin"
runat
=
"server"
></
telerik:RadSkinManager
>
<
telerik:RadInputManager
ID
=
"rimLogin"
runat
=
"server"
></
telerik:RadInputManager
>
<
telerik:RadFormDecorator
ID
=
"rfdLogin"
runat
=
"server"
/>
<
div
>
<
telerik:RadLightBox
ID
=
"RadLightBox1"
runat
=
"server"
></
telerik:RadLightBox
>
</
div
>
</
form
>
</
body
>
</
html
>