Recently, while upgrading an Asp.Net MVC 4 project someone created to an Asp.Net MVC 5 project, I ran across a great error. The error was this:
It was also bright and red!
Server Error in '/' Application.
Exception Details: System.InvalidCastException: [A]System.Web.WebPages.Razor.Configuration.HostSection cannot be cast to [B]System.Web.WebPages.Razor.Configuration.HostSection. Type A originates from 'System.Web.WebPages.Razor, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' in the context 'Default' at location 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.WebPages.Razor\v4.0_2.0.0.0__31bf3856ad364e35\System.Web.WebPages.Razor.dll'. Type B originates from 'System.Web.WebPages.Razor, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' in the context 'Default' at location 'C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\bc28c2e0\1b833c84\assembly\dl3\efd960b2\2bccde4f_7f44cf01\System.Web.WebPages.Razor.dll'.
This error made me VERY unhappy.
However, the solution was VERY simple.
I just needed to tell the application which version to use.
Here are the steps I took.
1. Open the web.config file.
2. Scroll until you find the <assemblybinding> tag under <runtime>.
3. Add in the following dependent assembly information for the dll that is causing you problems. In my case, it was as follows:
<dependentAssembly>
<assemblyIdentity name="System.Web.WebPages.Razor" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="2.0.0.0" newVersion="3.0.0.0"/>
</dependentAssembly>
4. Rebuild your project!
That is it! You should now see the fantastic work you have created after you build and Ctrl-F5. For all of you people out there still making projects with MVC 4 - JUST STOP! Back away slowly! MVC 5 is your friend!
Smooches,
Kila Morton
It was also bright and red!
Server Error in '/' Application.
[A]System.Web.WebPages.Razor.Configuration.HostSection cannot be cast to [B]System.Web.WebPages.Razor.Configuration.HostSection. Type A originates from 'System.Web.WebPages.Razor, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' in the context 'Default' at location 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.WebPages.Razor\v4.0_2.0.0.0__31bf3856ad364e35\System.Web.WebPages.Razor.dll'. Type B originates from 'System.Web.WebPages.Razor, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' in the context 'Default' at location 'C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\bc28c2e0\1b833c84\assembly\dl3\efd960b2\2bccde4f_7f44cf01\System.Web.WebPages.Razor.dll'.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.Exception Details: System.InvalidCastException: [A]System.Web.WebPages.Razor.Configuration.HostSection cannot be cast to [B]System.Web.WebPages.Razor.Configuration.HostSection. Type A originates from 'System.Web.WebPages.Razor, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' in the context 'Default' at location 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.WebPages.Razor\v4.0_2.0.0.0__31bf3856ad364e35\System.Web.WebPages.Razor.dll'. Type B originates from 'System.Web.WebPages.Razor, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' in the context 'Default' at location 'C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\bc28c2e0\1b833c84\assembly\dl3\efd960b2\2bccde4f_7f44cf01\System.Web.WebPages.Razor.dll'.
This error made me VERY unhappy.
However, the solution was VERY simple.
I just needed to tell the application which version to use.
Here are the steps I took.
1. Open the web.config file.
2. Scroll until you find the <assemblybinding> tag under <runtime>.
3. Add in the following dependent assembly information for the dll that is causing you problems. In my case, it was as follows:
<dependentAssembly>
<assemblyIdentity name="System.Web.WebPages.Razor" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="2.0.0.0" newVersion="3.0.0.0"/>
</dependentAssembly>
4. Rebuild your project!
That is it! You should now see the fantastic work you have created after you build and Ctrl-F5. For all of you people out there still making projects with MVC 4 - JUST STOP! Back away slowly! MVC 5 is your friend!
Smooches,
Kila Morton
