User authentication is a fundamental aspect of many web applications, and in today's interconnected world, users often prefer the convenience of using their existing social media or external accounts to sign in. In ASP.NET, setting up external login providers like Google, Facebook, or Twitter is a breeze. In this article, we'll walk through the process step-by-step and provide a working example.

Why Use External Login Providers?

External login providers offer several advantages for both developers and users:

• User Convenience: Users can log in using existing accounts, eliminating the need to remember yet another set of credentials.
• Security: External providers often implement robust security measures, reducing the risk of data breaches.
• Social Integration: Access to user profiles and social connections can enhance the user experience.

Step 1: Create a New ASP.NET Core Project

Begin by creating a new ASP.NET project in your preferred development environment, whether it's Visual Studio or Visual Studio Code.

Step 2: Configure External Authentication

In your project, open the Startup.cs file. Locate the ConfigureServices method, and add the following code to configure external authentication providers:

services.AddAuthentication().AddGoogle(options =>
{
    options.ClientId = "your-client-id";
    options.ClientSecret = "your-client-secret";
});

You can repeat this step for other providers like Facebook or Twitter, following the respective documentation for each provider to obtain the required client IDs and secrets.

Step 3: Configure External Login Middleware

Still in your Startup.cs file, find the Configure method and add the following code to enable the external login middleware:

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

Step 4: Create External Login Pages

Create pages for external login, registration, and callback handling. In your project, you can add Razor Pages or MVC views for these actions. For this example, let's create a simple Razor Page named ExternalLogin.cshtml.

Step 5: Add External Login Button

In your ExternalLogin.cshtml page, add buttons or links for each external provider you've configured. Here's an example for Google:

<a asp-area="Identity" asp-page="/Account/ExternalLogin" asp-route-provider="Google" class="btn btn-primary">Login with Google</a>

Step 6: Handle External Login Callback

In your project, create a callback method to handle the response from the external provider. In the AccountController.cs, add the following method:

public async Task<IActionResult> ExternalLoginCallback(string returnUrl = null, string remoteError = null)
{
    // Handle the callback and create or sign in the user as needed.
    return Redirect(returnUrl);
}

This method will receive the external provider's response, allowing you to create or sign in the user in your application.

Step 7: Test the External Login

Now, run your application and visit the ExternalLogin page. Click on the "Login with Google" button (or any other provider you've set up). You'll be redirected to the external provider's login page, and upon successful login, you'll be redirected back to your callback method.
 

Conclusion

Setting up external login providers in ASP.NET is a powerful way to enhance user authentication in your web application. Users appreciate the convenience, while developers benefit from the robust security and social integration these providers offer.

By following the steps outlined in this article and customizing them to your specific requirements, you can seamlessly integrate external login functionality into your ASP.NET project. Users will have the option to log in with their preferred external accounts, making your application more user-friendly and accessible.

Feel free to explore additional configuration options, such as obtaining user data from external providers and managing user roles and permissions, to further tailor the external login experience to your needs.