How to Use Microsoft Graph API to Access Outlook Mail in .NET

Introduction to Microsoft Graph API

• Microsoft Graph API is a unified API endpoint that enables access to Microsoft's cloud services. It's a gateway to data across various services, including Outlook Mail.

 

• This guide specifically helps you access Outlook Mail in a .NET application using Microsoft Graph API.

Set Up Your .NET Application

• Ensure your .NET application is set up. It should be registered in Azure, with the required permissions to access Microsoft Graph Outlook Mail.

 

• Install the Microsoft.Graph NuGet package to your .NET application.

dotnet add package Microsoft.Graph

Authenticate and Get an Access Token

• Use the Microsoft.Identity.Client library to handle authentication. This library can help you acquire the necessary access token with delegated permissions.

using Microsoft.Identity.Client;

// Initialize the public client application
var clientApp = PublicClientApplicationBuilder.Create(clientId)
                                               .WithAuthority(AzureCloudInstance.AzurePublic, tenantId)
                                               .WithRedirectUri(redirectUri)
                                               .Build();

// Define the scopes (permissions) to access
string[] scopes = { "Mail.Read" };

// Acquire the token
AuthenticationResult authResult = await clientApp.AcquireTokenInteractive(scopes).ExecuteAsync();

string accessToken = authResult.AccessToken;

Initialize the GraphServiceClient

• With the access token in hand, an instance of `GraphServiceClient` can be initialized, which is the main entry point for accessing data via Microsoft Graph.

using Microsoft.Graph;

// Pass the access token to the Graph Client
var graphClient = new GraphServiceClient(new DelegateAuthenticationProvider(async (requestMessage) =>
{
    requestMessage.Headers.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("bearer", accessToken);
}));

Access Outlook Mail

• Retrieve messages from Outlook using the `GraphServiceClient` instance. This example demonstrates fetching the top 10 unread messages.

// Get messages from the Inbox
var messages = await graphClient.Me.Messages
                                    .Request()
                                    .Filter("isRead eq false")
                                    .OrderBy("receivedDateTime DESC")
                                    .Top(10)
                                    .GetAsync();

// Read message details
foreach (var message in messages)
{
    Console.WriteLine($"Subject: {message.Subject}");
    Console.WriteLine($"From: {message.From.EmailAddress.Name}");
    Console.WriteLine($"Received: {message.ReceivedDateTime}");
}

Handle API Response and Errors

• Always incorporate error handling in your code to manage potential issues such as network errors, unauthorized responses, or data not found scenarios.

 

• Implement regular logging for monitoring API interactions, which provides insights into any problems that occur during the execution.

Maintain Security

• Ensure sensitive information such as client ID, client secrets, and access tokens are securely handled. Avoid hardcoding these values in your source code.

 

• Utilize Azure Key Vault or similar services to manage and protect credentials in a secure manner.