Introduction to Calling Microsoft Graph from a C# .Net Core Application

his post is a part of The Second Annual C# Advent.

Microsoft Graph is the unified API for any developers working with data inside Office 365, Azure Active Directory (Azure AD), Windows 10, and more.  In this post we’ll cover a quick introduction and share resources from 30 Days of Microsoft Graph blog series to show how to authenticate and to make calls against Microsoft Graph with C# and .Net Core (v2.1 as of the time of writing.)  Each of the referenced articles aims to take 5-15 mins to get you up to speed as quickly as possible while also providing hands-on exercises.  If you’d like to skip the background reading and start from scratch building a .Net Core console application that calls Microsoft Graph read through the README for the base-console-app within dotnetcore-console-sample.

 

Microsoft Graph overview

Microsoft Graph offers developers (and IT pros / admins) the ability to access data and insights in a number of services within Microsoft 365 services.  This includes:

  • Azure AD
  • Office 365 services
    • SharePoint
    • OneDrive
    • Outlook/Exchange
    • Microsoft Teams
    • OneNote
    • Planner
    • Excel
  • Enterprise Mobility and Security services
    • Identity Manager
    • Intune
    • Advanced Threat Analytics
    • Advanced Threat Protection
  • Windows 10 services
    • Activities
    • Devices
  • Education

By providing a unified endpoint for accessing all of these services Microsoft Graph removes a number of barriers including:

  • Discovering the service-specific endpoint URL
  • Authenticating to each endpoint separately
  • Managing different permission models
  • Working with incompatible data formats
  • …and more

All requests made to Microsoft Graph are sent as REST calls to https://graph.microsoft.com and leverage a common authentication model based on Azure AD and OAuth permissions along with a consent framework for users or admins.  The quickest way to see Microsoft Graph requests in action is to navigate to the Microsoft Graph explorer (https://aka.ms/ge, ge = Graph Explorer.)  For more information on using Graph Explorer please read Day 3 – Graph Explorer from the 30 Days of Microsoft Graph series.  Additionally you can make requests against Microsoft Graph using API development tools such as Postman.  Please read Day 13 – Postman to make Microsoft Graph requests for more information on using PostMan with Microsoft Graph.

 

Getting started sample

Seeing requests and their responses in a browser or tool is useful, but making requests in code or scripts is the more common scenario for usage.  In the examples below we will cover C# and .Net Core as .Net Core is available cross-platform, can be built in Visual Studio Code (also cross-platform), and offers many hosting options (console app, web app, serverless functions, and more.)

Authentication

All requests to Microsoft Graph require an authenticated context, either delegated or app-only.  Delegated is a union of the logged-in user’s context along with the application’s context.  App-only (as the name implies) is only the application’s context without any user involvement.  Please read Day 8 – Authentication roadmap and access tokens and Day 9 – Azure AD applications  on V2 endpoint for more information about creating an Azure AD application and getting an authenticated context.  On a similar note, you are highly encouraged to leverage Microsoft Authentication Library (MSAL) for creating your authentication context as this is the forward-focused version as opposed to the older Active Directory Authentication Library (ADAL).

Microsoft Graph SDK

While it is entirely possible to call the Microsoft Graph with an HttpClient (or similar) object, the Azure AD Identity and Microsoft Graph product groups recommend leveraging the Microsoft Graph SDK (Microsoft.Graph on Nuget.)  This SDK provides a number of benefits including:

  • Strongly typed entities and Microsoft Graph responses
  • Fluent API syntax
  • …and more

In future releases Microsoft Graph SDK will also provide abstractions for authentication prerequisites, automatic handling of retry logic or error handling, and more.

Sample solution

As mentioned at the beginning of this post if you’d like to build a working application from scratch (or clone the repo and configure the necessary settings) you can find the base-console-app within dotnetcore-console-sample.  Extracting the bare essential lines of code from this sample results in the following for authenticating to Microsoft Graph.

Note: If you do not see the below Gist please refer to code at this location: CS-Graph_Prepare_GraphServiceClient.cs

The following class implements the IAuthenticationProvider interface used for retrieving and then adding an Azure AD access token to subsequent requests to Microsoft Graph.  An out of the box implementation of this class will be provided at a later date within the Graph SDK.

Note: If you do not see the below Gist please refer to code at this location: CS-Graph_Class_MsalAuthenticationProvider.cs

Finally make a sample request to get a list of users within the Azure AD domain by calling Microsoft Graph.

Note: If you do not see the below Gist please refer to code at this location: CS-Graph_Request_Users_GraphServiceClient.cs

Conclusion

In this blog post we covered a quick introduction of Microsoft Graph and linked to additional resource within the 30 Days of Microsoft Graph blog series for additional background reading.  We also covered a barebones implementation of calling Microsoft Graph in a C# .Net Core console application.  Full instructions can be found on the base-console-app within dotnetcore-console-sample.  Thank you for reading along and please open an issue on GitHub repo if you run into any issues with the sample project.  Enjoy the rest of The Second Annual C# Advent.

 

-Frog Out

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