general System.Web.Razor error (also Postal project) - asp.net-mvc-4

Question

VS 2012, MVC4 app using Postal 0.8.0
When I NuGet install Andrew’s Davey’s Postal 0.8.0 it works on my development machine but when I deploy it I get this error message:
Could not load file or assembly 'System.Web.Razor, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.
I have spent several days trying to get this to work. What is the cause of this problem and how do you fix it?

Answer 1

When you install Postal with NuGet it replaces System.Web.Razor 2.0 with System.Web.Razor 1.0. I had to delete the reference to System.Web.Razor 1.0 and then added back in System.Web.Razor 2.0. You have to additionally set Copy Local to True in the Properties for System.Web.Razor and then rebuild the project. Once I did that VS2012 copied the System.Web.Razor.dll to the deployed bin directory and the problem cleared.
Postal also adds these dependency's to the web.config. I removed them and it still works properly.
<dependentAssembly>
<assemblyIdentity name="System.Web.Razor" publicKeyToken="31bf3856ad364e35" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-1.0.0.0" newVersion="2.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="WebGrease" publicKeyToken="31bf3856ad364e35" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-1.3.0.0" newVersion="1.3.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="RazorEngine" publicKeyToken="9ee697374c7e744a" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-3.0.8.0" newVersion="3.0.8.0" />
</dependentAssembly>
UPDATE 3/3/13
AD has just released Postal v0.8.2 which updated System.Web.Razor to 2.0.
The WebGrease dependency, with the release of ASP.NET and Web Tools 2012.2 (http://www.asp.net/vnext/overview/fall-2012-update) appears to be the default now.