C#: Could not load types from assembly

Question

After adding Lucene.net and Lucene.net Contrib to a C# MVC3, I get the message below after the first successful run. After receiving this error, I need to completely wipe C:\Users\Me\AppData\Local\Temp\Temporary ASP.NET Files before I can run the project again.

I've tried removing the Lucene files manually (including references in my project), and reinstalling them - both with NuGet and manually - but it's always the same situation; after the project has been run once, I start getting the following errors:

Note: Contrib.Regex is part of Lucene.net Contrib.

Server Error in '/' Application.

Could not load types from assembly Contrib.Regex, Version=2.9.4.0, Culture=neutral, PublicKeyToken=85089178b9ac3181, errors:
Exception: System.IO.FileLoadException: Could not load file or assembly 'Lucene.Net, Version=2.9.4.1, Culture=neutral, PublicKeyToken=85089178b9ac3181' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
File name: 'Lucene.Net, Version=2.9.4.1, Culture=neutral, PublicKeyToken=85089178b9ac3181'

=== Pre-bind state information ===
LOG: User = rcw7\Me
LOG: DisplayName = Lucene.Net, Version=2.9.4.1, Culture=neutral, PublicKeyToken=85089178b9ac3181
(Fully-specified)
LOG: Appbase = file:///C:/Development/Projects/Foobar/Foobar/
LOG: Initial PrivatePath = C:\Development\Projects\Foobar\Foobar\bin
Calling assembly : Contrib.Regex, Version=2.9.4.0, Culture=neutral, PublicKeyToken=85089178b9ac3181.
===
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Development\Projects\Foobar\Foobar\web.config
LOG: Using host configuration file: C:\Users\Me\Documents\IISExpress\config\aspnet.config
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework\v4.0.30319\config\machine.config.
LOG: Post-policy reference: Lucene.Net, Version=2.9.4.1, Culture=neutral, PublicKeyToken=85089178b9ac3181
LOG: Attempting download of new URL file:///C:/Users/Me/AppData/Local/Temp/Temporary ASP.NET Files/root/e9b4cfa4/edfa73f8/Lucene.Net.DLL.
WRN: Comparing the assembly name resulted in the mismatch: Revision Number
ERR: Failed to complete setup of assembly (hr = 0x80131040). Probing terminated.
Exception: System.IO.FileLoadException: Could not load file or assembly 'Lucene.Net, Version=2.9.4.1, Culture=neutral, PublicKeyToken=85089178b9ac3181' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
File name: 'Lucene.Net, Version=2.9.4.1, Culture=neutral, PublicKeyToken=85089178b9ac3181'

Full output here: http://pastebin.com/Vbu4VK7B

Initially I thought this was a problem local to my development environment, but after rebuilding and copying the project to our server, I get the same errors.

Any suggestions as how to overcome this? :-)

Answer 1

As it turns out, the DLL hell wasn't caused by my own meddling in configurations and compiled libraries. It was in fact caused by a collision between my newly downloaded version of Lucene.NET and a somewhat dated version bundled with Examine, which in turn was bundled with Umbraco 5.

Apparently the outdated, bundled Lucene.NET ended up in the shadow cache (Temporary ASP.NET Files), so after the next compile or IIS restart, execution would break. Clearing the shadow cache would allow for one success execution.

The weird thing was, that I was unable to find any reference anywhere in the debug output that hinted to the outdated version of Lucene.NET, either with a directory path or version number. The problem was spotted by comparing the file sizes of the shadow copied version of Lucene.NET and the version I intended to use. They were off, so I did a search for Lucene.NET.dll and found the one bundled with Examine in the Umbraco tree (under \App_Plugins\Examine)

The fast solution was to simply zip the Examine plugin, so Umbraco wouldn't see it. That leaves me without the Examine plugin, but I wasn't using it anyway.

The right solution would probably be to tell the app that it should ignore previous versions of Lucene.NET, but I haven't had any luck with that so far. This is what I added to web.config:

<dependentAssembly>
    <assemblyIdentity name="Lucene.Net" publicKeyToken="85089178b9ac3181" culture="neutral" />
    <bindingRedirect oldVersion="0.0.0.0-2.9.4.1" newVersion="2.9.4.1" />
</dependentAssembly>

This didn't seem to have any effect, and the outdated version still ended up in the shadow cache. I've moved this question here: How do I make Umbraco 5 ignore the bundled (with Examine) Lucene.NET

Thanks for your help and suggestions - it pointed me in the right direction! :-)

Answer 2

This normally means that you have the files in the GAC which are a different version and the ones in your bin are another version. So your application is pointing to a version and it is finding another. It is getting confused. What you want to do is uninstall Lucene.net. After you uninstall, look in the c:\windows\assembly folder and make sure there are no Lucene files in there. If there are, right click and uninstall. Then you can install again.