When I have a template page open in the VS editor, and run my Dynamic Data project, I immediately get an error that the page being edited can't be found, even when this is not the start page.
From this I gather the Dynamic Data runtime wants to write something to all pages, and I am very curious why. I'm sure it's nothing as droll as 'manually' adding dynamic controls to the source markup, but what could it be?
Take a look at the url when this occurs. If it's the path and name of the template file you went directly to this template without the proper url structure to route it correctly.
Actual path to file ->http://localhost:3760/MainFolder/DynamicData/PageTemplates/List.aspx
What it expects ->http://localhost:3760/MainFolder/TableName/List.aspx
This happens to me often when I right click on the template file and select view in browser. This just tells it to go directly to the file. Worked like a charm in Web Forms but now with routing the url has special meaning and going straight to the file causes the routing to fail.