System.TypeLoadException

[rvahitov]

Hi. I need your help. When running my application, I get the following error:
System.TypeLoadException: Could not load type 'ListExtensions' from assembly 'LanguageExt.Core, Version=5.0.0.0, Culture=neutral, PublicKeyToken=null'.

I searched the entire source code of LanguageExt.Core, but did not find a single type with this name.
I do not understand what the cause of the error could be.
I cleared the nugget cache, but the error did not disappear.
I am using LanguageExt.Core 5.0.0-beta-24.
Thanks in advance for any help.

[louthy]

First off make sure you're running the latest beta, there have been over 20 updates since that release.

Second, type-loads errors tend to happen when assembly references get 'out of sync', so check for mismatched assemblies or assembly redirects.

If the problem still persists, see if you can isolate it, because I'll need a bit more info than what you've provided so far.

[rvahitov]

Sorry, I made a mistake in the version number. (5.0.0-beta-54) Anyway, I'll try the second tip. Thanks.

[wolverine-ee]

I had the same issue when I brought in another library. I was using LanguageExt 5.0.0-beta-54. I received the same error: System.TypeLoadException: Could not load type 'ListExtensions' from assembly 'LanguageExt. Core, Version=5.0.0.0, Culture=neutral, PublicKeyToken=null'. When I checked the new library, it depended on LanguageExt 4.4.9. In this instance, I reverted to LanguageExt 4.4.9 with my code, which fixed the TypeLoadException.

[louthy]

The answer is the same. There isn't a type called ListExtensions in LanguageExt.Core. There used to be a type called ListExtensions in LanguageExt.Core. Therefore, if something is referring to ListExtensions in LanguageExt.Core then it is another (non language-ext) assembly that is dependent on the old version of LanguageExt.Core. Or, it is an assembly-redirect that is crossing major-version boundaries, which is always bad.

So, this is nothing to do with LanguageExt.Core, it is a dependency problem with other assemblies in your solution.

[rvahitov]

Found the reason for the exception. The third-party library (Akka.Persistence.Sql) that I use in the project uses LanguageExt.Core 4.4.9. Therefore, it cannot find the ListExtensions class.

[louthy]

Nice to see Akka using language-ext, but yep, that limits you to pre-v5 unfortunately

[rvahitov]

Unfortunately, this is true. Or don't migrate my project from Akka.Persistence.PostgresSql to Akka.Persistence.Sql until they move to v5