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Understanding Azure AD B2C authentication
Azure Active Directory Business to Consumer (Azure AD B2C) is a cloud identity management solution that allows you to authenticate users in your applications securely. With Azure AD B2C, you can manage your customer identities and provide a seamless sign-in experience while handling user authentication and authorization with ease. This guide will walk you through the steps to add Azure AD B2C authentication to your ASP.NET web application, ensuring you utilize the OpenID Connect protocol effectively.
Preparing your ASP.NET application
Before diving into the implementation, it’s essential to set up your development environment correctly. You can either start with an existing ASP.NET MVC project or create a new one. To start fresh, open your command shell and use the following command:
dotnet new mvc -n MyWebApp
This command initializes a new MVC project named MyWebApp. With your project in place, the next step is to incorporate the Microsoft Identity Web library, which simplifies the integration of Azure AD B2C authentication within your application.
Installing the necessary packages
To include the Microsoft Identity Web library, you’ll need to run the following commands in your project directory:
dotnet add package Microsoft.Identity.Web
dotnet add package Microsoft.Identity.Web.UI
These packages set up the authentication pipeline using cookie-based authentication, which handles HTTP authentication messages, token validation, and claims extraction automatically, allowing you to focus on developing your application.
Configuring the startup class
Open the Startup.cs file in your project. This file is crucial as it configures the services and middleware required for your application. At the top of this file, include the necessary namespaces:
using Microsoft.Identity.Web;
using Microsoft.Identity.Web.UI;
Next, you’ll need to modify the ConfigureServices method to set up the authentication services. Replace the existing method with the following code snippet:
services.AddAuthentication(OpenIdConnectDefaults.AuthenticationScheme)
.AddMicrosoftIdentityWebApp(Configuration.GetSection(“AzureAdB2C”));
By doing this, you’re informing the application to use Azure AD B2C for authentication. Also, don’t forget to configure the cookie policy as follows to ensure secure cookie handling:
services.Configure(options => {
options.CheckConsentNeeded = context => true;
options.MinimumSameSitePolicy = SameSiteMode.None;
});
Creating user interface components
To enhance user experience, it’s essential to implement UI elements that respond to user authentication status. You can achieve this by creating a partial view that checks whether the user is signed in. If not, it will display a sign-in button; if the user is signed in, it will show their display name along with a sign-out option.
Create a new file named _LoginPartial.cshtml within the /Views/Shared directory, and include the following code:
<div>
@if (User.Identity.IsAuthenticated) {
<p>Welcome, @User.Identity.Name!</p>
<a href=”/Account/Logout”>Sign out</a>
} else {
<a href=”/Account/Login”>Sign in</a>
}
</div>
Next, you’ll need to incorporate this partial view into your _Layout.cshtml file, which serves as the primary layout for your application. This layout includes common user interface components, ensuring a consistent user experience across pages.
Setting up claims handling
To view and manage the claims returned by the Azure AD B2C tokens, you need to create a new view under the /Views/Home directory named Claims.cshtml. This view will display the claims associated with the authenticated user.
Next, add a corresponding action in the HomeController.cs to link the claims view to its controller. Ensure this action is protected by the Authorize attribute, restricting access to authenticated users only:
[Authorize]
public IActionResult Claims() {
return View();
}
With these configurations, your application is well-equipped to handle user authentication through Azure AD B2C.
Finalizing your configuration
Finally, you must update your appsettings.json file to include your Azure AD B2C settings. This is vital for your application to authenticate users correctly. Add the following configuration:
{
“AzureAdB2C”: {
“Instance”: “https://.b2clogin.com/”,
“ClientId”: “”,
“Domain”: “”,
“SignUpSignInPolicyId”: “”,
“ResetPasswordPolicyId”: “”,
“EditProfilePolicyId”: “”
}
}
Replace the placeholders with your actual Azure AD B2C information. After the configuration is complete, users will see their display name in the navigation bar upon successful authentication, and they can access their claims through the Claims action.