Instantiate AzureBlogStorage Binder C# isolated-process Function

Question

Based on this Microsoft example, this so answer and this blog post I can get declarative bindings to compile. At runtime, I get a System.NullReferenceException: Object reference not set to an instance of an object from the binder.

I've tried moving the Binder to constructor. I've tried both Binder and IBinder and dug through a ton of docs. Can someone point me in the right direction?

Function

public class BeaconIngestion
    {
        private readonly ILogger<BeaconIngestion> _logger;

        public BeaconIngestion(ILogger<BeaconIngestion> logger )
        {
            _logger = logger;

        }

        [Function(nameof(BeaconIngestion))]
        [StorageAccount("DATA_STORAGE_ACCOUNT_CONNECTION_STRING")]
        public async Task Run([EventHubTrigger("messages/events", Connection = "IOTHUB_CONNECTION_STRING") ] EventData[] events,
                Binder binder)
        {
            foreach (EventData _event in events)  //leading underscore because 'event is a keyword.
            {
                string message =  System.Text.Encoding.UTF8.GetString(_event.Body.ToArray());
                _logger.LogInformation("Event Body: {body}", message);
                _logger.LogInformation("Event Content-Type: {contentType}", _event.ContentType);
                string path = $"landing/{DateTime.UtcNow.ToString("yyyy/MM/dd/HH_mm_ss")}data.json";
                _logger.LogInformation("Sending data to {path} using binder {binder}", path, binder);
                using (var writer = await binder.BindAsync<TextWriter>(new BlobAttribute(path, FileAccess.Write)))
                {
                    writer.Write("Hello World");
                }
            
            }
        }
    }

host.json

    "logging": {
        "applicationInsights": {
            "samplingSettings": {
                "isEnabled": true,
                "excludedTypes": "Request"
            },
            "enableLiveMetricsFilters": true
        }
    },
    "extensions": {
        "blobs": {
            "maxDegreeOfParallelism": 4,
            "poisonBlobThreshold": 2 
        }
    }
}

local.settins.json

{
    "IsEncrypted": false,
    "Values": {
        "AzureWebJobsStorage": "UseDevelopmentStorage=true",
        "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
        "IOTHUB_CONNECTION_STRING": "<connectionstring>",
        "DATA_STORAGE_ACCOUNT_CONNECTION_STRING" : "<connectionstring>"
    }
}

Program.cs

using Microsoft.Extensions.Hosting;

var host = new HostBuilder()
    .ConfigureFunctionsWorkerDefaults()
    .Build();

host.Run();

Answer 1

AFAIK, IBinder and Binder can't be used in isolated function as they are the attributes of Microsoft.Azure.WebJobs and also confirmed by product team in this github issue.

Alternatively, I have used the below code to write the data into Blob storage using BlobContainerClient attribute.

Code:

using System;
using Azure.Messaging.EventHubs;
using Azure.Storage.Blobs;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;

namespace FunctionApp33
{
    public class Function1
    {
        private readonly ILogger<Function1> _logger;

        public Function1(ILogger<Function1> logger)
        {
            _logger = logger;
        }

        [Function(nameof(Function1))]
        public async Task Run([EventHubTrigger("samples-workitems", Connection = "EventHub_ConnectionString")] EventData[] events,
            BlobContainerClient blobContainerClient)
        {
            foreach (EventData @event in events)
            {
                _logger.LogInformation("Event Body: {body}", @event.Body);
                _logger.LogInformation("Event Content-Type: {contentType}", @event.ContentType);
                var blobServiceClient = new BlobServiceClient("Storage account connection string");

                //Create a unique name for the container
                string containerName = "demo";

                // Create the container and return a container client object
                blobContainerClient = await blobServiceClient.CreateBlobContainerAsync(containerName);

                // Create a local file in the ./data/ directory for uploading and downloading
                string localPath = "data";
                Directory.CreateDirectory(localPath);
                string fileName = "test.txt";
                string localFilePath = Path.Combine(localPath, fileName);

                // Write text to the file
                await File.WriteAllTextAsync(localFilePath, "Hello, World!");

                // Get a reference to a blob
                BlobClient blobClient = blobContainerClient.GetBlobClient(fileName);

                Console.WriteLine("Uploading to Blob storage as blob:\n\t {0}\n", blobClient.Uri);

                // Upload data from the local file
                await blobClient.UploadAsync(localFilePath, true);
            }
        }
    }
}

Output:

References: Quickstart: Azure Blob Storage library - .NET | Microsoft Learn.