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>
I had to update AzureFunctionsVersion from v3 to v4. That solved the issue.
Upgrading Azure Functions wasn't mentioned in the official migration guide from Microsoft.
EDIT: you also need to upgrade the Azure Function App as well.