Razor Host Factory error

Question

I get a MvcWebRazorHostFactory error trying to run my app, but it's not an MVC app at all. I have the following web packages installed via nuget:

Microsoft ASP.NET Razor
Microsoft ASP.NET Web API 2.1
Microsoft ASP.NET Web Pages

My app is angularjs front end using razor views (.cshtml). I don't understand why I keep getting this error.

An exception of type 'System.InvalidOperationException' occurred in System.Web.WebPages.Razor.dll but was not handled in user code

Additional information: Could not locate Razor Host Factory type: System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=5.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35

And here is the razor section in my web.config:

<system.web.webPages.razor>
<host factoryType="System.Web.WebPages.Razor.WebRazorHostFactory, System.Web.WebPages.Razor, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
<pages pageBaseType="System.Web.WebPages.WebPage">
  <namespaces>
    <add namespace="System.Web.Configuration" />
    <add namespace="System.Web.Optimization" />
    <add namespace="System.Web.Routing" />
  </namespaces>
</pages>

Answer 1

I resolved this issue by setting System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc Version to 5.2.0.0 and it worked, finally! Why 5.2.0.0? Same version as NuGet Microsoft ASP.NET project.

So, the line in /Views/Web.Config should be:

<host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=5.2.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />

Answer 2

For the benefit of anyone developing ASP.NET MVC 5 web apps using Xamarin Studio v5.5.3 on OSX, deleting the /Views/Web.config did not work for me and created other errors.

To fix it, open /Views/Web.config and change all instances of 5.2.0.0 to 5.2.2.0

More details here

Answer 3

Several of the answers point in the right direction, but I was not sure where in the Microsoft Visual Studio for Mac interface I could find the appropriate version number to use for the version part of the factoryType attribute.

For the benefit of other VS for Mac users, the answer is to simply right-click on the Microsoft.AspNet.Mvc package in the Packages list in the solution explorer.

In my case, the package version was "5.2.6" after a package update, so I set the version part of the factoryType attribute to Version=5.2.6.0. This solved the problem.

Answer 4

Changed the version of MvcWebRazorHostFactory to the same version of System.Web.Mvc which resolved my issue.

Answer 5

So apparently some package I got from nuget adds a web.config to the Views folder. In this web.config there were settings for the MvcWebRazorHostFactory. I think this occurred when I added a View to my project using the dialog box.

The solution is to remove the web.config from the Views folder.

Answer 6

I started getting this error in my Razor .cshtml pages in an MVC project following some NuGet package management / upgrading.

I didn't want to remove the Web.config file completely from the Views folder because I had customised it width some <add namespace="..." /> elements. But I noticed that the Version=... in the <host factoryType="..." /> didn't match my version of System.Web.Mvc (checked version in Object Browser).

Altering this version number to match that of my System.Web.Mvc assembly, and restarting Visual Studio, fixed the problem for me (as suggested by Daniel)

Answer 7

This happened to me today. I just made sure the version number for the web.config in the views folder matches the version number for the web.config of the solution.

Hope this helps.

Answer 8

For MacBook users having the Visual Studio 2019, you simply go to the Web.config file and update version of the System.Web.Mvc to that which is in your Nuget packages folder.

Answer 9

1. Inside your Web project, open "References" tree node.
   2. Look for "Assemblies" folder and open it.
   3. Look for System.Web.Mvc, right click on it, and select "Properties"

A dialog will prompt, read carefully the package full name field and look for the version number. For example, I have this one:

System.Web.Mvc, Version=5.2.7.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35

So, in the Web.config (inside Views folder) replace the version number!

In my case, it originally was:

<host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=5.2.2.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />

Now I have (look at the Version value):

<host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=5.2.7.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />

Hope it helps!