In my Solution I have three projects. Project A is a web app and uses version 1.0.10618.0 of the AjaxControlToolkit. I would love to upgrade it to the latest but unfortunately any newer release completely breaks a portion of my site.

Project B is also a web app but is a completely new software product and so it uses (and relies on) the latest version of the AjaxControlToolkit. Everything works great.

Thought A and B are totally different products they use the same DB and rely on the same ClassLibrary. Project C is a small web app that ties A and B together with certain functionality like forgot password pages. The pages in this app reside in a virtual directory of both A and B. Project C currently uses v1.0.10618.0 of the toolkit so it works with Project A but it fails with project B because the manifest definitions of the dlls don't match (to be expected).

What I've done is built a new dll of the toolkit and changed the assembly and namespace to AjaxControlToolkit_v1 and then changed all v1 references to this new dll so the old version and new versions can sit side by side in the same bin folder and nobody complains. I then changed my web.config controls tag to look like this:

<add tagPrefix="ajaxToolkit" namespace="AjaxControlToolkit_v1" assembly="AjaxControlToolkit_v1, Version=1.0.10618.0, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e"/>

This all works except I get a runtime error of: Unknown server tag 'ajaxToolkit:AnimationExtender'.

I can't figure out why this is, any ideas on how to remedy it?