Unlocking the Power of Azure AD B2C Authentication in ASP.NET Core: A Step-by-Step Guide

Are you tired of juggling multiple authentication systems for your ASP.NET Core application? Do you want to provide a seamless and secure experience for your users? Look no further! In this comprehensive guide, we’ll show you how to implement Azure AD B2C authentication in an ASP.NET Core application that has Razor pages and web API in a single application.

What is Azure AD B2C?

Azure Active Directory B2C (Azure AD B2C) is a cloud-based identity and access management solution that enables you to customize and control how users sign up, sign in, and manage their profiles. It provides a scalable and secure way to authenticate users in your application, while also providing features like password reset, account blocking, and more.

Why Choose Azure AD B2C?

• Customizable and flexible authentication flows
• Support for multiple identity providers (Google, Facebook, LinkedIn, and more)
• Advanced security features, such as multi-factor authentication and conditional access
• Easy integration with ASP.NET Core applications
• Scalable and reliable, with a 99.99% uptime SLA

Prerequisites

Before we dive into the implementation, make sure you have the following:

• Azure AD B2C tenant and a registered application
• ASP.NET Core 3.1 or later
• Razor pages and web API in a single application
• Visual Studio 2019 or later

Step 1: Install the Required NuGet Packages

In your ASP.NET Core project, install the following NuGet packages:

Install-Package Microsoft.AspNetCore.Authentication.AzureADB2C.UI
Install-Package Microsoft.AspNetCore.Authentication.OpenIdConnect
Install-Package Microsoft.Identity.Web

Step 2: Configure Azure AD B2C

In your Azure AD B2C tenant, create a new application and configure the following settings:

Setting	Value
Web App/ API	Yes
Reply URL	https://localhost:5001/signin-oidc
Logout URL	https://localhost:5001/signout-oidc

Make a note of the Client ID and Tenant ID, as we’ll need them later.

Step 3: Configure the Authentication Middleware

In your ASP.NET Core project, add the following code to the `Startup.cs` file:

using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.AzureADB2C.UI;
using Microsoft.AspNetCore.Authentication.OpenIdConnect;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;

public void ConfigureServices(IServiceCollection services)
{
    services.AddAuthentication(options =>
    {
        options.DefaultChallengeScheme = "AzureADB2C";
        options.DefaultSignInScheme = "AzureADB2C";
    })
    .AddAzureADB2C(options =>
    {
        options.ClientId = Configuration["AzureAdB2C:ClientId"];
        options.TenantId = Configuration["AzureAdB2C:TenantId"];
        options.Instance = "https://{your_tenant_name}.b2clogin.com/tfp/{your_tenant_name}.onmicrosoft.com/{your_policy_name}";
        options.SignUpSignInPolicyId = "{your_policy_id}";
        options.ResetPasswordPolicyId = "{your_policy_id}";
    });
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseRouting();
    app.UseAuthentication();
    app.UseAuthorization();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapRazorPages();
        endpoints.MapControllers();
    });
}

Replace `{your_tenant_name}`, `{your_policy_name}`, and `{your_policy_id}` with your Azure AD B2C tenant name, policy name, and policy ID, respectively.

Step 4: Add Authentication to Razor Pages

Update your Razor pages to use the Azure AD B2C authentication middleware:

@page
@attribute [Authorize]
@using Microsoft.AspNetCore.Authorization

// Your Razor page content here

This will require users to authenticate before accessing the Razor page.

Step 5: Add Authentication to Web API

Update your web API controllers to use the Azure AD B2C authentication middleware:

[ApiController]
[Route("api/[controller]")]
[Authorize]
public class MyController : ControllerBase
{
    // Your API controller actions here
}

This will require users to authenticate before accessing the web API.

Step 6: Implement Sign-in and Sign-out

Create a new Razor page for sign-in and sign-out:

@page "/signin"
@attribute [AllowAnonymous]

Sign In

@page "/signout" @attribute [Authorize] @using Microsoft.AspNetCore.Authentication

Sign Out

@code { [Authorize] public async Task OnPostAsync() { await HttpContext.SignOutAsync("AzureADB2C"); return RedirectToPage("/Index"); } }

This will allow users to sign in and sign out of your application using Azure AD B2C.

Conclusion

And that’s it! You’ve successfully implemented Azure AD B2C authentication in your ASP.NET Core application with Razor pages and web API. This will provide a secure and scalable way to authenticate users in your application, while also providing advanced features like multi-factor authentication and conditional access.

Remember to replace the placeholders with your actual Azure AD B2C tenant name, policy name, and policy ID. If you encounter any issues, refer to the Azure AD B2C documentation and ASP.NET Core authentication middleware documentation for more information.

Additional Resources

• Azure AD B2C documentation: https://docs.microsoft.com/en-us/azure/active-directory-b2c/
• ASP.NET Core authentication middleware documentation: https://docs.microsoft.com/en-us/aspnet/core/security/authentication/?view=aspnetcore-3.1

Happy coding!

Frequently Asked Question

Are you trying to implement Azure Active Directory B2C (AAD B2C) authentication on your ASP.NET Core application that has Razor pages and web API in a single application? Look no further! Here are some frequently asked questions to get you started.