I have defined an Azure IoT DPS, with an enrollment group, that calls a Custom allocation policy function, this function should set initialDeviceTwin tags, I have tried to implement this function as described in https://learn.microsoft.com/en-us/azure/iot-dps/tutorial-custom-allocation-policies

With TwinCollection as the type for the tags – that did not work i.e no DeviceTwin tags was set, then I changed the implementation to:

    [Function("DeviceIoTHubAllocationFunc")]
    public async Task<IActionResult> Run([HttpTrigger(AuthorizationLevel.Anonymous,"post")]  HttpRequest req)
    {
        _logger.LogInformation("C# HTTP trigger function processed a request.");
        string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
        dynamic data = JsonConvert.DeserializeObject(requestBody);
    
        // Get registration ID of the device
        string regId = data?.deviceRuntimeContext?.registrationId;
    
        string message = "Uncaught error";
        bool fail = false;
    
        _logger.LogInformation("Request.Body:...");
        _logger.LogInformation(requestBody);
    
        ResponseObj obj = new ResponseObj();
        Response response = null;
        //ProvisioningServiceResponse response = null;
    
        if (regId == null)
        {
            message = "Registration ID not provided for the device.";
            _logger.LogInformation("Registration ID : NULL");
            fail = true;
        }
        else
        {
            _logger.LogInformation("RegID");
            _logger.LogInformation(regId);
    
            string[] hubs = data?.linkedHubs?.ToObject<string[]>();
    
            // Must have hubs selected on the enrollment
            if (hubs == null)
            {
                message = "No hub group defined for the enrollment.";
                _logger.LogInformation("linkedHubs : NULL");
                fail = true;
            }
    
            _logger.LogInformation("Before get IoTHubModel");
            _logger.LogInformation(regId);
            var model = _repository.GetBySerialNumber(regId);
            _logger.LogInformation("After get IoTHubModel");
            _logger.LogInformation(model.HubHostName);
    
            
            if (model is not null && hubs.Any(h => h.Equals(model.HubHostName)))
            {
                
                response = new Response(model.HubHostName);
    
                response.initialTwin.tags = new JObject
                {
                    ["enrolled"] = model.Enrolled,
                    ["regional"] = "eus2",
                };
            }
            else
            {
                message = "Unknown hubhost";
                _logger.LogInformation($"Expected Hub host name : {model?.HubHostName ?? "NULL"}");
                fail = true;
            }
        }
    
    
        _logger.LogInformation("nResponse");
        _logger.LogInformation((response.iotHubHostName != null) ?   JsonConvert.SerializeObject(response) : message);
    
        return (fail)
            ? new BadRequestObjectResult(message)
            : (ActionResult)new OkObjectResult(response);            
    }
    
    
    public class Response
    {
        public Response(string hostName)
        {
            iotHubHostName = hostName;
            initialTwin = new ResponseTwin();
        }
    
        public string iotHubHostName { get; set; }
        public ResponseTwin initialTwin { get; set; }
    }
    
    public class ResponseTwin
    {
        public ResponseTwin()
        {
            properties = new ResponseProperties();
        }
    
        public dynamic tags { get; set; }
        public ResponseProperties properties { get; set; } // contains desired properties
    }
    
    public class ResponseProperties
    {
        public dynamic desired { get; set; }
    }
    

The log output from the function was:
Request: “……….., initialTwin”:{“tags”:{},”properties”:{“desired”:{}}}
Response: {“iotHubHostName”:”MYHUB.azure-devices.net”,”initialTwin”:{“tags”:{“enrolled”:true,”region”:”eus2″},”properties”:{“desired”:null}}}

When I inspect the device twin the following tags are set:

    "tags": {
        "enrolled": [],
        "region": []
    },

What am I doing wrong – and any guesses why the Microsoft.Azure.Devices.Shared.TwinState and TwinCollection doesn’t work

Thanks

Described in the sections above