.NET 8 ISOLATED Azure Function - Binding attributes not working

I am porting an old .NET 6 in-process Azure Function app, to .NET 8 isolated worker model. I have an issue where it seems like the app configuration expression resolution for our Azure Function bindings no longer works in .NET 8 isolated.

For instance, this BlobTrigger function used to look like this with .NET 6 in-process:

public async Task Run([BlobTrigger(
    "%StorageContainer:SourceImages%/{name}")]
BlobClient blob)

We had an app setting for %StorageContainer:SourceImages% in local.settings.json:

...
"StorageContainer:SourceImages": "mycontainer",
....

The blob trigger would use the built in .NET expression resolution stuff, to grab the StorageContainer.SourceImages value, stick it in the trigger attribute, and everything worked great.

Now, in .NET 8 isolated worker, I have to change my function parameters / trigger information a bit.

[Function("PhotoDataIndexer")]
public async Task Run([BlobTrigger(
    "mycontainer/{name}",
    Connection = "BlobFuncConnectionString")]
string stream, string name)

This works, it's picking up the blobs.

However, I do not want to have to supply the container name mycontainer directly in the function definition. I want to keep using my app setting reference of %StorageContainer:SourceImages% to grab the name.

Is this not possible in .NET 8 isolated worker model?

You can use the same method in Isolated-process model.

This worked for me.

using System;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace FunctionApp16
{
    public class Function2
    {
        private readonly ILogger<Function2> _logger;

        public Function2(ILogger<Function2> logger)
        {
            _logger = logger;
        }

        [Function(nameof(Function2))]
        public void Run([BlobTrigger("%StorageContainer:SourceImages%", Connection = "AzureWebJobsStorage")] string message)
        {
            _logger.LogInformation($"C# Queue trigger function processed: {message}");
        }
    }
}

FunctionApp16.csproj:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <OutputType>Exe</OutputType>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <FrameworkReference Include="Microsoft.AspNetCore.App" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.20.1" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.16.4" />
    <PackageReference Include="Microsoft.ApplicationInsights.WorkerService" Version="2.21.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.ApplicationInsights" Version="1.1.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Storage.Blobs" Version="6.3.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http.AspNetCore" Version="1.2.0" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
  <ItemGroup>
    <Using Include="System.Threading.ExecutionContext" Alias="ExecutionContext" />
  </ItemGroup>
</Project>

Program.cs:

using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

var host = new HostBuilder()
    .ConfigureFunctionsWebApplication()
    .ConfigureServices(services =>
    {
        services.AddApplicationInsightsTelemetryWorkerService();
        services.ConfigureFunctionsApplicationInsights();
    })
    .Build();

host.Run();

local.settings.json:

{
    "IsEncrypted": false,
    "Values": {
        "AzureWebJobsStorage": "UseDevelopmentStorage=true",
        "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
        "StorageContainer:SourceImages": "test"
  }
}

OUTPUT: