Connect an ASP.NET Core app to Microsoft 365
In this unit, you’ll learn how to authenticate an application to connect to Microsoft Graph to securely access data from Microsoft 365.
Authenticate to access data from Microsoft 365
Microsoft Graph is a REST API that exposes data and insights stored in Microsoft 365. This information isn't available publicly. To gain access, users must (a) prove their identity (authentication) and (b) consent to allow your application to access their data. This is the job of Microsoft Entra ID.
Your application needs to get an access token from Microsoft Entra ID and include that in each request to Microsoft Graph. You can think of the access token like a movie ticket: your application uses the OAuth protocol to obtain a ticket and then presents the ticket to the attendant (Microsoft Graph) to get into the movie (the secured resources in Microsoft 365).
Once identity is set up, people can sign in to your app using their existing Microsoft 365 account. This frees you from having to implement authentication in your app and maintain users’ credentials. It also benefits people by not having to use yet another credential to access your app. What’s more, it allows organizations to control their employees’ access to different applications, which is an important requirement these days.
Connect to Microsoft 365 by using SDKs
Both Microsoft Entra ID and Microsoft Graph are REST services, so in theory you could retrieve calendar events using direct HTTP requests. However, to make it easier, Microsoft offers two Software Development Kits (SDKs) that handle the requests for you. These SDKs take care of building requests and handling exceptions, allowing you to focus on building your app.
| Service | SDK |
|---|---|
| Microsoft Entra ID | Microsoft Authentication Library (MSAL) |
| Microsoft Graph | Microsoft Graph SDK |
MSAL handles the details of the OAuth protocol with Microsoft Entra ID. Using MSAL your application will let users sign in with their Microsoft 365 account and consent to any permissions your application needs. Once they’re signed in, MSAL will provide the access token that you need to communicate with Microsoft Graph.
To simplify the process of working with MSAL, ASP.NET Core applications can take advantage of an assembly named Microsoft.Identity.Web. This assembly abstracts MSAL functionality and simplifies the overall process of integrating it into your applications.
Next steps
Let’s start by running a simple app connected to Microsoft 365 that shows the name of the user and their profile picture retrieved from Microsoft 365.