Exercise 3: Microsoft Graph track changes (delta query)

In this exercise, you’ll learn how to use the track changes capability in Microsoft Graph. The track changes capability, also called delta query, enables applications to get a list of all items that have been added, updated, or deleted since the last time the same query was issued.

You’ll then implement track changes with the existing change notifications code to create a responsive application that only sends requests to Microsoft Graph when entities change and only retrieves those entities that changed. This process results in fewer requests to Microsoft Graph and receives smaller payloads from Microsoft Graph, making it be more performant application.

[!IMPORTANT] This exercise assumes you have created the Azure AD application and .NET console application from the previous unit in this module. You’ll edit the existing Azure AD application and .NET console application created in that exercise in this exercise.

Task 1: Update the ASP.NET Core web API project

  1. Locate and open the following controller: Controllers > NotificationsController.cs. Add the following code to the existing NotificationsController class.

  2. This code includes a new method, CheckForUpdates(), that will call the Microsoft Graph using the delta url and then pages through the results until it finds a new deltalink on the final page of results. It stores the url in memory until the code is notified again when another notification is triggered.

private static object? DeltaLink = null;
private static IUserDeltaCollectionPage? lastPage = null;

private async Task CheckForUpdates()
{
  var graphClient = GetGraphClient();

  // get a page of users
  var users = await GetUsers(graphClient, DeltaLink);

  OutputUsers(users);

  // go through all of the pages so that we can get the delta link on the last page.
  while (users.NextPageRequest != null)
  {
    users = users.NextPageRequest.GetAsync().Result;
    OutputUsers(users);
  }

  object? deltaLink;

  if (users.AdditionalData.TryGetValue("@odata.deltaLink", out deltaLink))
  {
    DeltaLink = deltaLink;
  }
}

private void OutputUsers(IUserDeltaCollectionPage users)
{
  foreach (var user in users)
  {
    var message = $"User: {user.Id}, {user.GivenName} {user.Surname}";
    Console.WriteLine(message);
  }
}

private async Task<IUserDeltaCollectionPage> GetUsers(GraphServiceClient graphClient, object? deltaLink)
{
  IUserDeltaCollectionPage page;

  if (lastPage == null || deltaLink == null)
  {
    page = await graphClient.Users
                            .Delta()
                            .Request()
                            .GetAsync();
  }
  else
  {
    lastPage.InitializeNextPageRequest(graphClient, deltaLink.ToString());
    page = await lastPage.NextPageRequest.GetAsync();
  }

  lastPage = page;
  return page;
}
  1. Locate the existing Post() method and replace it with the following code:
public async Task<ActionResult<string>> Post([FromQuery] string? validationToken = null)
{
  // handle validation
  if (!string.IsNullOrEmpty(validationToken))
  {
    Console.WriteLine($"Received Token: '{validationToken}'");
    return Ok(validationToken);
  }

  // handle notifications
  using (StreamReader reader = new StreamReader(Request.Body))
  {
    string content = await reader.ReadToEndAsync();

    Console.WriteLine(content);

    var notifications = JsonSerializer.Deserialize<ChangeNotificationCollection>(content);

    if (notifications != null)
    {
      foreach (var notification in notifications.Value)
      {
        Console.WriteLine($"Received notification: '{notification.Resource}', {notification.ResourceData.AdditionalData["id"]}");
      }
    }
  }

  // use deltaquery to query for all updates
  await CheckForUpdates();

  return Ok();
}

  1. The Post method will now call CheckForUpdates when a notification is received.

  2. Save all files.

Test your changes

  1. Within Visual Studio Code, select Run > Start debugging to run the application.

  2. Navigate to the following url: http://localhost:5000/api/notifications. This will register a new subscription.

  3. Open a browser and navigate to the Microsoft 365 admin center (https://admin.microsoft.com/AdminPortal).

  4. If you’re prompted to sign-in, sign-in using an admin account.

  5. Select Users > Active users.

  6. Select an active user and select Edit for their Contact information.

  7. Update the Mobile phone value with a new number and Select Save.

  8. Wait for the notification to be received as indicated in the Visual Studio Code Debug Console:

Received notification: 'Users/7a7fded6-0269-42c2-a0be-512d58da4463', 7a7fded6-0269-42c2-a0be-512d58da4463
  1. The application will now start a delta query with Microsoft Graph to get all the users and log out some of their details to the console output.
User: 19e429d2-541a-4e0b-9873-6dff9f48fabe, Allan Deyoung
User: 05501e79-f527-4913-aabf-e535646d7ffa, Christie Cline
User: fecac4be-76e7-48ec-99df-df745854aa9c, Debra Berger
User: 4095c5c4-b960-43b9-ba53-ef806d169f3e, Diego Siciliani
User: b1246157-482f-420c-992c-fc26cbff74a5, Emily Braun
User: c2b510b7-1f76-4f75-a9c1-b3176b68d7ca, Enrico Cattaneo
User: 6ec9bd4b-fc6a-4653-a291-70d3809f2610, Grady Archie
User: b6924afe-cb7f-45a3-a904-c9d5d56e06ea, Henrietta Mueller
User: 0ee8d076-4f13-4e1a-a961-eac2b29c0ef6, Irvin Sayers
User: 31f66f05-ac9b-4723-9b5d-8f381f5a6e25, Isaiah Langer
User: 7ee95e20-247d-43ef-b368-d19d96550c81, Johanna Lorenz
User: b2fa93ac-19a0-499b-b1b6-afa76c44a301, Joni Sherman
User: 01db13c5-74fc-470a-8e45-d6d736f8a35b, Jordan Miller
User: fb0b8363-4126-4c34-8185-c998ff697a60, Lee Gu
User: ee75e249-a4c1-487b-a03a-5a170c2aa33f, Lidia Holloway
User: 5449bd61-cc63-40b9-b0a8-e83720eeefba, Lynne Robbins
User: 7ce295c3-25fa-4d79-8122-9a87d15e2438, Miriam Graham
User: 737fe0a7-0b67-47dc-b7a6-9cfc07870705, Nestor Wilke
User: a1572b58-35cd-41a0-804a-732bd978df3e, Patti Fernandez
User: 7275e1c4-5698-446c-8d1d-fa8b0503c78a, Pradeep Gupta
User: 96ab25eb-6b69-4481-9d28-7b01cf367170, Megan Bowen
User: 846327fa-e6d6-4a82-89ad-5fd313bff0cc, Alex Wilber
User: 200e4c7a-b778-436c-8690-7a6398e5fe6e, MOD Administrator
User: 7a7fded6-0269-42c2-a0be-512d58da4463, Adele Vance
User: 752f0102-90f2-4b8d-ae98-79dee995e35e,   Removed?:deleted
User: 4887248a-6b48-4ba5-bdd5-fed89d8ea6a0,   Removed?:deleted
User: e538b2d5-6481-4a90-a20a-21ad55ce4c1d,   Removed?:deleted
User: bc5994d9-4404-4a14-8fb0-46b8dccca0ad,   Removed?:deleted
User: d4e3a3e0-72e9-41a6-9538-c23e10a16122,   Removed?:deleted

  1. In the Microsoft 365 Admin Portal, repeat the process of editing a user and Save again.

  2. The application will receive another notification and will query Microsoft Graph again using the last delta link it received. However, this time you’ll notice that only the modified user was returned in the results.

User: 7a7fded6-0269-42c2-a0be-512d58da4463, Adele Vance
  1. Using this combination of notifications with delta query you can be assured you won’t miss any updates to a resource. Notifications may be missed because of transient connection issues, however the next time your application gets a notification it will pick up all the changes since the last successful query.

Summary

In this exercise, you learned how to use the track changes capability in Microsoft Graph. The track changes capability, also called delta query, enables applications to get a list of all items that have been added, updated, or deleted since the last time the same query was issued.

You then implemented track changes with the existing change notifications code to create a responsive application that only sends requests to Microsoft Graph when entities change and only retrieves those entities that changed. This process results in fewer requests to Microsoft Graph and receives smaller payloads from Microsoft Graph, making it be more performant application.