Authentication in Azure App Console and query in the Microsoft Graph application

Question

Hello, thank you for all the advice you have been able to provide me in these groups following the guides and blogs. I'm having issues with authentication and queries. I tried to follow the exercise provided by Microsoft and reached this point.

1. graphHelper.cs

using System.Diagnostics;
using Azure.Core;
using Azure.Identity;
using Microsoft.Graph;
using Microsoft.Graph.Models;
//-----------------------------------------------
//Aqui se configura todo el acceso de autenticacion a la aplicacion
[DebuggerDisplay($"{{{nameof(GetDebuggerDisplay)}(),nq}}")]
class GraphHelper
{
    // Esta configira el aceso que se encuentra ne el archivo .jason appsettings
    private static Settings? _settings;
    // Credenciales de autenticacion del usuario 
    private static DeviceCodeCredential? _deviceCodeCredential;
    // configuracion del cliente con el usuario de autenticacion
    private static GraphServiceClient? _userClient;

    public static void InitializeGraphForUserAuth(Settings settings,
    Func<DeviceCodeInfo, CancellationToken, Task> deviceCodePrompt)
    {
    _settings = settings;

        var options = new DeviceCodeCredentialOptions
         {
            ClientId = settings.ClientId,
            TenantId = settings.TenantId,
            DeviceCodeCallback = deviceCodePrompt,
        };

        _deviceCodeCredential = new DeviceCodeCredential(options);

        _userClient = new GraphServiceClient(_deviceCodeCredential, settings.GraphUserScopes);
    }

    public static async Task<string> GetUserTokenAsync()
    {
        // Ensure credential isn't null
        _ = _deviceCodeCredential ??
        throw new System.NullReferenceException("Graph has not been initialized for user auth");

        // Ensure scopes isn't null
        _ = _settings?.GraphUserScopes ?? throw new System.ArgumentNullException("Argument 'scopes' cannot be null");

        // Request token with given scopes
        var context = new TokenRequestContext(_settings.GraphUserScopes);
        var response = await _deviceCodeCredential.GetTokenAsync(context);
        return response.Token;
    }
    //----------------------------------------------------------------------
    public static Task<Device?> GetUserAsync()
    {
        // Ensure client isn't null
        _ = _userClient ??
            throw new System.NullReferenceException("Graph has not been initialized for user auth");

        return _userClient.Devices.GetAsync((config) =>
        {
            // Only request specific properties
            config.QueryParameters.Select = new[] {"displayName", "deviceId"};
        });
    }

    private string GetDebuggerDisplay()
    {
        return ToString();
    }
}

2. program.cs

Console.WriteLine("Dispositivos\n");
var settings = Settings.LoadSettings();

//Inincializacion de MS graph
InitializeGraph(settings);

//Greet he user by name
await GreetUserAsync();

int choice = -1;

while (choice != 0)
{
    Console.WriteLine("Seleccione una de las siguiente sopciones");
    Console.WriteLine("0. Exit");
    Console.WriteLine("1. Display access token");

    try
    {
        choice = int.Parse(Console.ReadLine() ?? string.Empty);
    }
    catch (System.FormatException)
    {
        // Set to invalid value
        choice = -1;
    }

    switch(choice)
    {
        case 0:
            // Exit the program
            Console.WriteLine("Adios...");
            break;
        case 1:
            // Display access token
            await DisplayAccessTokenAsync();
            break;
        default:
            Console.WriteLine("Opcion no valida");
            break;
    }
}
    void InitializeGraph(Settings settings)
{
    GraphHelper.InitializeGraphForUserAuth(settings,
        (info, cancel) =>
        {
            // Display the device code message to
            // the user. This tells them
            // where to go to sign in and provides the
            // code to use.
            Console.WriteLine(info.Message);
            return Task.FromResult(0);
        });
}
{
    // TODO
}

async Task GreetUserAsync()
{
    try
    {
        var devicePerson = await GraphHelper.GetUserAsync();
        Console.WriteLine($"Nombre Dispositivo, {device?.DisplayName}!");
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Error getting devicePerson: {ex.Message}");
    }
}

async Task DisplayAccessTokenAsync()
{
    try
    {
        var userToken = await GraphHelper.GetUserTokenAsync();
        Console.WriteLine($"User token: {userToken}");
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Error getting user access token: {ex.Message}");
    }
}

I have followed this exercise and other tutorials: https://learn.microsoft.com/en-us/graph/tutorials/dotnet?tutorial-step=2&tabs=aad. Thanks