Could not load file or assembly 'System.Text.Encoding.CodePages, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

[shibayan]

Repro steps

Provide the steps required to reproduce the problem:

1. Create function app project
2. Install System.Text.Encoding.CodePages nuget package
3. Adding Encoding.RegisterProvider(CodePagesEncodingProvider.Instance); to function
4. Run function app

Expected behavior

Function app is executed without error

Actual behavior

The following error occurs and the function cannot be executed.

[2021-01-15T07:00:17.378Z] A host error has occurred during startup operation 'e356b46a-f0fb-44a1-8494-df0ad91f3d36'.
[2021-01-15T07:00:17.380Z] FunctionApp34: Could not load file or assembly 'System.Text.Encoding.CodePages, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. 指定されたファイルが見つかりません。.
Value cannot be null. (Parameter 'provider')

Known workarounds

• Adding _FunctionsSkipCleanOutput setting
• Downgrade System.Text.Encoding.CodePages to v4.7.1

[lars-erik]

I have the same problem. The publish targets remove a lot of stuff.
The System.Text.Encoding.CodePages.dll is copied into bin/runtime/netstandard2.0.
It seems like files under bin/runtime/** are not probed at all.
I've tried this with both V2 and V3 runtime, including pretty much all framework targets since netstandard2.0.

I managed to get the file copied to the bin folder locally with an extra target in my .csproj, but I couldn't figure which target / filegroup / property to use in order to include the file in the .zip that is published.
So for now I grudgingly copy the file into the function's bin folder using the kudu console.

Let me know if I can help by providing more details. Here's my targets:

  <Target Name="ForceCopyCodePages" AfterTargets="_FunctionsBuildCleanOutput">
    <Message Importance="High" Text="Copying messed up deps to $(OutputPath)" />
    <Copy SourceFiles="$(OutputPath)bin\runtimes\win\lib\netcoreapp2.0\System.Text.Encoding.CodePages.dll"
          DestinationFolder="$(OutputPath)bin"/>
  </Target>
  <Target Name="ForcePublishCodePages" AfterTargets="_FunctionsPostPublish">
    <Message Importance="High" Text="Copying messed up deps for publish to $(PublishDir)bin" />
    <Copy SourceFiles="$(OutputPath)bin\runtimes\win\lib\netcoreapp2.0\System.Text.Encoding.CodePages.dll"
          DestinationFolder="$(PublishDir)bin"/>
  </Target>

[v-bbalaiagar]

Hi @shibayan, Apologies for the delayed response, please let us know if you were able to find a solution to this, if not, we would like to reproduce your project to understand the error better, could you give us the repro steps or test Zip file if possible which can repro the error.

This issue has been automatically marked as stale because it has been marked as requiring author feedback but has not had any activity for 4 days. It will be closed if no further activity occurs within 3 days of this comment.

[shibayan]

@v-bbalaiagar The workaround is described in the first comment.
The root cause of this problem is that the Azure Functions SDK deletes any assembly with a matching name without considering the assembly version. It is necessary to delete the assembly only if it is the same or lower version than the assembly that Functions Runtime has, and not delete it if it is a larger version.