typeof(Sys) === 'undefined' error when running ASP.NET app

Question

I am developing a Web Application using WebForms with ASP.NET. Using a ScriptManager, I am loading a custom javascript script file.

When I view the page in browser, I do not get the intended action (display a timer) and "view source" on the page gives me the following error message:

//<![CDATA[
if (typeof(Sys) === 'undefined') throw new Error('ASP.NET Ajax client-side framework failed to load.');
//]]>

In my attempts to troubleshoot, I have used the same javascript file in an ASP.NET Website and it works fine. It only seems to happen with a Web Application. I've also added an alert into my javascript file, which works fine on both Website and Web Application.

Possible duplicate of this [question](http://stackoverflow.com/questions/75322/sys-is-undefined) — Anna Brenden, May 02 '12 at 11:26
Eric: The question you've linked to uses in-line javascript. I'm using a ScriptManager. But thanks. — Vim, May 02 '12 at 11:28
One of the answers to that question talks about using a ScriptManager — Anna Brenden, May 02 '12 at 11:31
Kris: Any particular option I need to run Aspnet_regiis.exe with? — Vim, May 02 '12 at 11:54
Does you web.config include a link to `System.Web.Extensions`? — cjk, May 02 '12 at 12:09
All I needed to do was change the following Web.config from to A huge thank you to everyone who contributed! — Vim, May 02 '12 at 12:50

score 0 · Answer 1 · answered May 02 '12 at 12:07

There are two possible reasons for this error.

First is that you do not have include the ScriptManager, but because as you say you have included it, the second reason is that you need to move the ScriptManager before the call of the "sys" so can be found by the rest script that throw this error.

So move the ScriptManager upper, or move your script lower than ScriptManager.

typeof(Sys) === 'undefined' error when running ASP.NET app

1 Answers1