I got the go-ahead to move the ListSearchExtender from the prototype branch of the AJAX Control Toolkit to the development branch, and everything was going swimmingly until I got this error when running:
Assembly 'AjaxControlToolkit, Version=1.0.10201.0, Culture=neutral, PublicKeyToken=28f01b0e84b6d53e' contains a Web resource with name 'AjaxControlToolkit.ListSearchBehavior.js', but does not contain an embedded resource with name 'AjaxControlToolkit.ListSearchBehavior.js'.
I checked, and yes my ListSearchBehavior.js file did have its Build Action property set to Embedded Resource so the solution wasn’t that easy.
Next I fired up the ildasm tool that comes with the .NET SDK and double-clicked on the manifest. Here I got a clue as to what was happening. It showed that the embedded resource was called AjaxControlToolkit.ListSearchBehavior.ListSearchBehavior.js whereas all the others were called things like AjaxControlToolkit.DropShadow.DropShadowBehavior.js
I went digging in my code and sure enough, I’d screwed up my assembly and ClientScriptResource attributes. This is the corrected version (the bold bits used to say ListSearchBehavior):
public class ListSearchExtender : ExtenderControlBase
Hopefully this post will save others that are banging their heads against the wall with the same error.