MVC3 deploy - Could not load file or assembly 'System.Web.WebPages.Razor, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies

Whilst deploying my newly upgraded ASP.NET MVC 3 web application to the production environment I started receiving a FileNotFoundException with the error message "Could not load file or assembly 'System.Web.WebPages.Razor, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified." I have encountered this before so I know it is about bin-deploying that assembly. But where is the System.Web.WebPages.Razor assembly?

Since you have installed ASP.NET MVC 3 on your development machine you have all these MVC 3 assemblies installed in your GAC. Your production machine does not!

So you need to find this file and make it bin deployable however this cheeky assembly isn't in you solution so how can you do that? Well... add it. Go to Add Reference on your root web project (e.g. Web.csproj) and find System.Web.WebPages.Razor and add.

Now right click this assembly in your references directory and click properties.

Now you can make it bin deployable by setting Copy Local to true like so:

Note this is how to deploy the System.Web.WebPages.Razor assembly withe your ASP.NET MVC 3 web application. To deploy a typical setup of an ASP.NET MVC 3 app you will need to do the same for all of the following assemblies:

• System.Web.Mvc
• System.Web.Helpers
• System.Web.Razor
• System.Web.WebPages
• System.Web.WebPages.Deployment
• System.Web.WebPages.Razor as detailed above
• Microsoft.Web.Infrastructure this will also need a reference added as above
• WebMatrix.Data this also needs the reference

Of course you only need to add the reference to these assemblies if they are not already there - in most cases it will be. This was mainly a blog post for the slightly more complicated System.Web.WebPages.Razor.dll

Update

There is an easier way to do this if you are using Visual Studio 2010 Service Pack 1 and using Web Deploy as your publish action when publishing. You can add deployable dependencies to your ASP.NET MVC project that will choose the necessary assemblies for you. Even easier!