.NET Azure Active Directory B2C Integration

A complete guide to integrating Azure Active Directory B2C with .NET applications, covering configuration, authentication, and best practices.

Table of Contents

• Introduction to Azure Active Directory B2C
• Why Use Azure AD B2C?
• Prerequisites
• Setting Up Azure AD B2C
• Integrating Azure AD B2C with .NET
• Custom Policies in Azure AD B2C
• Best Practices
• Conclusion

Introduction to Azure Active Directory B2C

Azure Active Directory B2C (Azure AD B2C) is a cloud-based identity management solution for consumer-facing applications. It allows developers to implement secure authentication, user registration, and profile management in their applications.

Why Use Azure AD B2C?

Azure AD B2C offers the following advantages for .NET applications:

• Scalable and secure identity management.
• Customizable user flows for login, signup, and password reset.
• Supports various identity providers like Google, Facebook, and Microsoft accounts.
• Easy integration with .NET applications using Microsoft.Identity.Web library.
• GDPR and compliance-ready for global users.

Prerequisites

Before starting the integration, ensure you have the following:

• An active Azure subscription.
• A .NET 6.0+ application.
• Basic understanding of OAuth 2.0 and OpenID Connect protocols.

Setting Up Azure AD B2C

Follow these steps to set up Azure AD B2C:

Step 1: Create an Azure AD B2C Tenant

1. Log in to the Azure portal.
2. Search for "Azure Active Directory B2C" and create a new tenant.

Step 2: Register an Application

1. In the B2C tenant, navigate to "App registrations" and register your .NET application.
2. Configure the redirect URI to match your application’s callback endpoint (e.g., https://localhost:5001/signin-oidc).

Integrating Azure AD B2C with .NET

Step 1: Install Required NuGet Packages

dotnet add package Microsoft.Identity.Web
dotnet add package Microsoft.Identity.Web.UI
            

Step 2: Update appsettings.json

{
  "AzureAdB2C": {
    "Instance": "https://<tenant-name>.b2clogin.com/",
    "ClientId": "<application-id>",
    "Domain": "<tenant-name>.onmicrosoft.com",
    "SignUpSignInPolicyId": "B2C_1_SignUpSignIn"
  }
}
            

Step 3: Configure Middleware in Program.cs

var builder = WebApplication.CreateBuilder(args);

// Add Azure AD B2C authentication
builder.Services.AddAuthentication(OpenIdConnectDefaults.AuthenticationScheme)
    .AddMicrosoftIdentityWebApp(builder.Configuration.GetSection("AzureAdB2C"));

builder.Services.AddControllersWithViews();

var app = builder.Build();

app.UseAuthentication();
app.UseAuthorization();

app.MapDefaultControllerRoute();
app.Run();
            

Custom Policies in Azure AD B2C

Azure AD B2C allows developers to define custom user flows for advanced scenarios like:

• Multi-factor authentication (MFA).
• Custom identity provider integration.
• Progressive profiling.

Custom policies can be created using XML-based policy files and uploaded via the Azure portal.

Best Practices

• Enable logging to debug authentication issues.
• Use HTTPS for secure communication between your application and Azure AD B2C.
• Test all user flows in different environments before deployment.
• Keep secrets like Client IDs and Keys in Azure Key Vault.

Conclusion

Azure AD B2C is a robust solution for managing user authentication in .NET applications. By following this guide, you can securely integrate Azure AD B2C with your .NET application and enhance its identity management capabilities.

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