Monday, 18 January 2010

ASP.Net MVC's Hidden Web.Config File

I've just spent some time banging my head against a virtual brick wall built by my Build Server. It has, for some time now, been successfully building and deploying 2 versions (v1 and v2) of the same 'White Labelled' website to an internal testing web server. Recently I edited the definition so that it deleted all v2 files on the testing server before deploying. I did this because MVC Views that the developers had deleted, moved or renamed were remaining in the deployment and causing problems.

So, both versions were absolutely identical except for their web.config files that targeted different databases.

Both sites would allow me to hit the landing and login; but v2 failed to render any view that was strongly typed against a ViewModel. For instance, a view that inherited this would be fine...


... however, a view that inherited this, would fail...


The exception was a System.Web.HttpParseException: "Could not load type 'MyApp.MyViewModel'".

Turns out that it was because I wasn't deploying that innocuous little web.config file that resides in the root View directory. One very important part of this file is to deny direct browsing to the aspx & ascx files - you want any requests to go via your routing model and controllers. The second purpose is to define the base types for your views and how to parse them.

Bottom line: without it your app won't work.

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