.NET 6 System.IO.FileNotFoundException：无法加载文件或程序集 System.Linq，版本 = 6.0.0.0

Question

I am trying to migrate a project from .NET Core 3.1 to .NET 6. I have followed the official migration guide from Microsoft .

During build in startup.Configure I get

System.IO.FileNotFoundException: 'Could not load file or assembly 'System.Linq, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.'

This is.csproj:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <AzureFunctionsVersion>v3</AzureFunctionsVersion>
    <AssemblyName>Omicron.Insurance.Runner</AssemblyName>
    <RootNamespace>Omicron.Insurance.Runner</RootNamespace>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Omicron.Insurance.Entities" Version="1.0.139" />
    <PackageReference Include="Omicron.Platform.Web.ApplicationInsights" Version="3.1.60" />
    <PackageReference Include="Microsoft.Azure.Functions.Extensions" Version="1.1.0" />
    <PackageReference Include="Microsoft.Azure.ServiceBus" Version="5.2.0" />
    <PackageReference Include="Microsoft.Extensions.Configuration.AzureKeyVault" Version="3.1.22" />
      <PackageReference Include="Microsoft.EntityFrameworkCore" Version="6.0.1" />
      <PackageReference Include="Microsoft.EntityFrameworkCore.Proxies" Version="6.0.1" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="4.0.1" />
    <PackageReference Include="NodaTime" Version="3.0.9" />
    <PackageReference Include="ServiceBus.AttachmentPlugin" Version="6.2.0" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
</Project>

Answer 1

I had to update AzureFunctionsVersion to v4 from v3 . That solved the issue

Answer 2

My case is different from the OP's but I want to share it for information. I run into this error when I try to use dnSpy to patch a C# DLL. It turns out the dnSpy compilation is targeting dependencies of my development machine. When I move the compiled DLL to the target machine, this error is raised as the dependencies are not met there. I have to compile it again on my target machine and the error is gone.