For even the mildly curious, this begs a question: Can ASP.NET AJAX and SharePoint 2007 work together? For now, the answer is "Yes, but…" with a few caveats.
The catch? Official SharePoint support for ASP.NET AJAX will only arrive with SharePoint 2007 Service Pack 1, Ammeraan said. This is because Microsoft shipped SharePoint 2007 while ASP.NET AJAX was still in beta. (Mary Jo Foley reports that Vista SP1 should arrive by the end of 2007.)
The lack of a Service Pack, though, need not deter developers from integrating the two technologies now, Ammerann noted. Such an integration requires three steps -- installing ASP.NET AJAX onto your server farm, extending SharePoint's web.config files and adding the ASP.NET AJAX Script Manager into your master page. Ammerann provides instructions for all three steps, along with a hint for making the Update Panel work inside SharePoint 2007.
Meanwhile, development tools for integrating ASP.NET AJAX and SharePoint 2007 are beginning to emerge in the blogosphere.
Eric Schoonover has created a base class called AjaxBasePart, which "custom MOSS [Microsoft Office SharePoint Server] Web parts can derive from and fully enables all AJAX Extensions functionality within MOSS." Additional information about AjaxBasePart, and its source code, can be found in Schoonover's blog entry, AjaxBasePart: Easy ASP.NET 2.0 AJAX Extensions 1.0 and Office SharePoint Server 2007.
Jan Tielens has created a SmartPart, or SharePoint Web part, which allows developers to use ASP.NET AJAX extensions inside a Web User Control and run that control as a SharePoint Web part. Put simply, the SmartPart lets you build Ajax-style controls for SharePoint. This add-in, still in beta, can be downloaded from the SmartPart for SharePoint page on GotDotNet, and additional information and demos are available on Tielens' blog entry, SmartPart for SharePoint -- ASP.NET AJAX Support.
Daniel Larson has created the SharePoint Ajax Toolkit, which comes with SharePoint Solution Package based installer, a Refresh interval programmed into an XMLWebPart and a core framework.
Finally, Tielens offers some quick hints for using the ASP.NET AJAX Control Toolkit with SharePoint 2007.