.NET get DeviceId from Microsoft.Azure.Devices.Client.ModuleClient

Question

I would like to get the assigned device-id from Microsoft.Azure.Devices.Client.ModuleClient assigned from the IoT-Hub to my module.

What is the best way to retrieve the device-id at runtime?

Answer 1

So we have to make use of a back-end solution to Read Module Twin Properties, like deviceId. This is by design, you have to make use of Back end app as stated in following Document : Module twins , Inside the Module App only Desired and Reported are available.

Please refer to Get started with IoT Hub module identity and module twin (.NET)

Sample Console C# app : Make use of 'registryManager' to query all devices with the query language. The query functionality is exposed by the C# service SDK in the RegistryManager class.

var query = registryManager.CreateQuery("SELECT * FROM devices", 100);

Complete sample console C# code snippet is as shown below. [using Microsoft.Azure.Devices;]

using Microsoft.Azure.Devices;
using Microsoft.Azure.Devices.Common.Exceptions;
using Newtonsoft.Json;
using System;
using System.Threading.Tasks;

namespace CreateIds
{
    class Program
    {
        const string connectionString ="<>";     
        static void Main(string[] args)
        {
            GetDeviceIdAsync().Wait();
        }
        private static async Task GetDeviceIdAsync()
        {
            RegistryManager registryManager =
              RegistryManager.CreateFromConnectionString(connectionString);
            try
            {
                
                var query = registryManager.CreateQuery("SELECT * FROM devices", 100);
                while (query.HasMoreResults)
                {
                    var page = await query.GetNextAsTwinAsync();
                    foreach (var twin in page)
                    {
                        Console.WriteLine(JsonConvert.SerializeObject(twin.DeviceId));
                    }
                }
            }
            catch (DeviceAlreadyExistsException dvcEx)
            {
                Console.WriteLine("Error : {0}", dvcEx);
            }

        }
    }
}

Update 1: Using 'Where' clause to get deviceId Example json twin from devices.modules looks like the below one. Now we have to query by using 'Where' clause like moduleId='sampleModule'

Sample:{"deviceId":"devkitdps","moduleId":"sampleModule","etag":"AAAAAAAAAAE=","version":4,"status":"enabled","statusUpdateTime":"0001-01-01T00:00:00Z","connectionState":"Disconnected","lastActivityTime":"0001-01-01T00:00:00Z","cloudToDeviceMessageCount":0,"authenticationType":"sas","x509Thumbprint":{"primaryThumbprint":null,"secondaryThumbprint":null},"properties":{"desired":{"$metadata":{"$lastUpdated":"0001-01-01T00:00:00Z"},"$version":1},"reported":{"DateTimeLastAppLaunch":"2020-06-23T17:22:19.4938255-07:00","$metadata":{"$lastUpdated":"2020-06-24T00:22:19.6523448Z","DateTimeLastAppLaunch":{"$lastUpdated":"2020-06-24T00:22:19.6523448Z"}},"$version":3}}}

  var query = registryManager.CreateQuery("SELECT * FROM devices.modules Where moduleId='sampleModule'", 100);
                while (query.HasMoreResults)
                {
                    var page = await query.GetNextAsTwinAsync();
                    foreach (var twin in page)
                    {
                        Console.WriteLine(JsonConvert.SerializeObject(twin.DeviceId));
                    }
                }

Please let us know if you need further help!