in my previous sample i talked about creating custom expression encoder templates. good times. also jesse alluded to a something him and i have been working on with regard to what he calls "hyper video" and what i've previously referred to as 'timed overlays' in an example.
in going through both of these i found an issue that i forgot to write about (but a helpful commenter reminded me: thanks ernie!) with regard to using the expression encoder templates and asp.net ajax.
expression encoder uses a model of encapsulating silverlight and the media elements within an asp.net ajax control. because they do that, they include the Microsoft AJAX client library (MicrosoftAjax.js) in the template output. this poses a problem when you implement their code within an asp.net page that already has asp.net ajax in it!
if you don't make any changes and have a ScriptManager in your code in addition to the template output, you'll see errors like Sys._application, yada yada.
the solution is two part.
first, you'll notice that in your expression encoder output you'll see the script reference to MicrosoftAjax.js. if you are including a ScriptManager on your page for other ajax-ness, then you can remove this. why? well because ScriptManager brings down the MicrosoftAjax.js file for you automatically (read: trust me, you don't need it).
<asp:ScriptManager id="sm" runat="server">
<asp:ScriptReference Path="~/Silverlight.js" />
<asp:ScriptReference Path="~/BasePlayer.js" />
<asp:ScriptReference Path="~/PlayerStrings.js" />
<asp:ScriptReference Path="~/player.js" />
<asp:ScriptReference Path="~/StartPlayer.js" />
this is only necessary if you have expression encoder template output as well as you are implementing asp.net ajax content on your page/application.
hope this helps.