Build API clients for .NET with Microsoft identity authentication

In this tutorial, you generate an API client that uses Microsoft identity authentication to access Microsoft Graph.

Required tools

• .NET SDK 8.0

Create a project

Run the following command in the directory you want to create a new project.

dotnet new console -o GetUserClient
dotnet new gitignore

Add dependencies

Before you can compile and run the generated API client, you need to make sure the generated source files are part of a project with the required dependencies. Your project must have a reference to the abstraction package. Additionally, you must either use the Kiota default implementations or provide your own custom implementations of the following packages.

• Authentication (Kiota default Azure authentication)
• HTTP (Kiota default HttpClient-based implementation)
• Form serialization (Kiota default)
• JSON serialization (Kiota default)
• Text serialization (Kiota default)
• Multipart serialization (Kiota default)

For this tutorial, use the default implementations.

Run the following commands to get the required dependencies.

dotnet add package Microsoft.Kiota.Abstractions
dotnet add package Microsoft.Kiota.Http.HttpClientLibrary
dotnet add package Microsoft.Kiota.Serialization.Form
dotnet add package Microsoft.Kiota.Serialization.Json
dotnet add package Microsoft.Kiota.Serialization.Text
dotnet add package Microsoft.Kiota.Serialization.Multipart
dotnet add package Microsoft.Kiota.Authentication.Azure
dotnet add package Azure.Identity

Generate the API client

Kiota generates API clients from OpenAPI documents. Create a file named get-me.yml and add the following.

openapi: 3.0.3
info:
  title: Microsoft Graph get user API
  version: 1.0.0
servers:
  - url: https://graph.microsoft.com/v1.0/
paths:
  /me:
    get:
      responses:
        200:
          description: Success!
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/microsoft.graph.user"
components:
  schemas:
    microsoft.graph.user:
      type: object
      properties:
        id:
          type: string
        displayName:
          type: string

You can then use the Kiota command line tool to generate the API client classes.

kiota generate -l csharp -d get-me.yml -c GetUserApiClient -n GetUserClient.ApiClient -o ./Client

Register an application

To be able to authenticate with the Microsoft identity platform and get an access token for Microsoft Graph, you need to create an application registration. You can install the Microsoft Graph PowerShell SDK and use it to create the app registration, or register the app manually in the Azure Active Directory admin center.

The following instructions register an app and enable device code flow for authentication.

Connect-MgGraph -Scopes "Application.ReadWrite.All"
$app = New-MgApplication -displayName "Kiota Test Client" -IsFallbackPublicClient

> $app.AppId
1cddd83e-eda6-4c65-bccf-920a86f220ab

Create the client application

The final step is to update the Program.cs file that was generated as part of the console application to include the following code. Replace YOUR_CLIENT_ID with the client ID from your app registration.

using Azure.Identity;
using GetUserClient.ApiClient;
using Microsoft.Kiota.Authentication.Azure;
using Microsoft.Kiota.Http.HttpClientLibrary;

// The auth provider will only authorize requests to
// the allowed hosts, in this case Microsoft Graph
var allowedHosts = new [] { "graph.microsoft.com" };
var graphScopes = new [] { "User.Read" };

var options = new DeviceCodeCredentialOptions
{
    ClientId = "YOUR_CLIENT_ID",
    DeviceCodeCallback = (code, cancellation) =>
    {
        Console.WriteLine(code.Message);
        return Task.FromResult(0);
    },
};

var credential = new DeviceCodeCredential(options);

var authProvider = new AzureIdentityAuthenticationProvider(credential, allowedHosts, scopes: graphScopes);
var requestAdapter = new HttpClientRequestAdapter(authProvider);
var client = new GetUserApiClient(requestAdapter);

var me = await client.Me.GetAsync();
Console.WriteLine($"Hello {me.DisplayName}, your ID is {me.Id}");

Run the application

To start the application, run the following command in your project directory.

dotnet run

See also

• kiota-samples repository contains the code from this guide.
• ToDoItem Sample API implements a sample OpenAPI in ASP.NET Core and sample clients in multiple languages.