After upgrading from VS2005 to VS2008 I run into a problem viewing my pages in design mode. The error message displayed in the designer is:
Master Page error
The Master Page file 'http://localhost/MainProject/Page.Master' cannot be loaded.
Correct the problem in Code view.
This problem occurs for projects that are nested. For example:
The application consists out of two projects, one MainProject and one SubProject, and the bin folder from the MainProject is used for both assemblies.
The MainProject works fine and the use of the Master Page file located in the root (as described in the error above) works fine.
For the SubProject (located: http://localhost/MainProject/SubProject) the designer gives the error message like above.
I created this Main/Sub setup to see if the error could be reproduced and to make sure it wasn't generated during project conversion from VS2005 to VS2008. Unfortunately the error persists.
Some other things where tried to see if the error coud be resolved/worked around. I tried including the MainProject's assembly in the SubProject's references, I tried to change the Master Page location to 'C:\inetpub\wwwroot\MainProject\Page.Master', I tried to recreate the SubProject's pages by using the 'Web Content Form' template from the 'Add New Item' templates by first creating a dummy Master Page in the SubProject and changing that after.
Unfortunately, none of these attempts gave me a working solution.
Building both projects and opening them in the browser displays the projects just fine. The problem lies in the VS2008 designer view.