program.cs

using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Authentication.OpenIdConnect;
using Microsoft.IdentityModel.Protocols.OpenIdConnect;
using Microsoft.Extensions.Configuration;

IConfiguration Configuration = new ConfigurationBuilder()
    .SetBasePath(AppDomain.CurrentDomain.BaseDirectory)
    .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
    .Build();

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllersWithViews();

// Connect to Asgardeo for authentication.
builder.Services.AddAuthentication(options => {
    options.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
    options.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;
})
.AddCookie()
.AddOpenIdConnect(options =>
{
    options.SignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;
    options.ClientId = Configuration["Asgardeo:ClientID"];
    options.ClientSecret = Configuration["Asgardeo:ClientSecret"];
    options.Authority = $"https://api.asgardeo.io/t/{Configuration["Asgardeo:Tenant"]}/oauth2/token";
    options.ResponseType = OpenIdConnectResponseType.Code;
    options.ResponseMode = OpenIdConnectResponseMode.Query;
    options.SaveTokens = true;
    options.Scope.Add("profile");
    options.Scope.Add("openid");
});

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    app.UseExceptionHandler("/Home/Error");
    // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
    app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();

app.UseRouting();

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

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}");

app.Run();