Getting Started with Auth0 in ASP.NET

What is Auth0?

Why would you want to add authentication to your ASP.NET project?

Making a project:

using System.Net;
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllersWithViews();
var text = "Hello World!";
var app = builder.Build();
app.UseDeveloperExceptionPage();
app.UseRouting();
app.UseEndpoints(endpoints => {
    endpoints.MapGet("/", () => "/read Reads the text\n/write?new_text Writes the text to be read.");
    endpoints.MapGet("/read", () => text);
    endpoints.MapGet("/write", context =>
    {
        if (context.Request.QueryString.HasValue)
        {
            text = WebUtility.UrlDecode(context.Request.QueryString.Value?.Substring(1));
        }
        context.Response.Redirect("/read");
        return Task.CompletedTask;
    });
});
app.Run();

"launchUrl": "",

/read Reads the test 
/write?new_text Writes the text to be read.

Adding authentication with Auth0:

using Auth0.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.OAuth;
using System.Net;

var builder = WebApplication.CreateBuilder(args);

builder.Services
    .AddAuth0WebAppAuthentication(configureOptions =>
    {
        configureOptions.CallbackPath = new PathString("/logged-in"); // URL must be added to API settings, for example: http://localhost:5092/logged-in

        // These should be in another file (such as appsettings.json) and loaded into this one, but for simplicity they are being hard coded.
        configureOptions.ClientId = "l2DofA5ooVteRXwoYEVPSZ8cEu6CSASX";
        configureOptions.ClientSecret = "21yH9ajaCCJL_i0fUHU2mM8DLELIZC1Rz3Fi-JWASPylE4S_bNdFGTSplZsfphYG"; // Always keep hidden.
        configureOptions.Domain = "dev-egllimpvthky2sob.us.auth0.com";
    });

builder.Services.AddControllersWithViews();

var text = "Hello World!";

var app = builder.Build();

app.UseDeveloperExceptionPage();

app.UseRouting();

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

app.UseEndpoints(endpoints => {

    endpoints.MapGet("/", () => "/read Reads the text\n/write?new_text Writes the text to be read.");

    endpoints.MapGet("/read", () => text).RequireAuthorization();

    endpoints.MapGet("/write", context =>
    {
        if (context.Request.QueryString.HasValue)
        {
            text = WebUtility.UrlDecode(context.Request.QueryString.Value?.Substring(1)); // Remove the ? at the start of the query string.
        }
        context.Response.Redirect("/read");
        return Task.CompletedTask;
    }).RequireAuthorization();

    // Default ASP login path.

    endpoints.MapGet("/Account/AccessDenied", context =>
    {
        context.Response.Redirect("/");
        return Task.CompletedTask;
    });

    endpoints.MapGet("/Account/Login", async context =>
    {
        var authenticationProperties = new LoginAuthenticationPropertiesBuilder()
        .Build();

        await context.ChallengeAsync(Auth0Constants.AuthenticationScheme, authenticationProperties);
    });

    endpoints.MapGet("/Account/Logout", async context =>
    {
        var authenticationProperties = new LogoutAuthenticationPropertiesBuilder()
        .Build();

        await context.ChallengeAsync(Auth0Constants.AuthenticationScheme, authenticationProperties);
    });
});

app.Run();