Program.cs

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddReverseProxy().LoadFromConfig(builder.Configuration.GetSection("ReverseProxy"));

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

// Add System.Web adapter services, including registering remote app authentication
builder.Services.AddSystemWebAdapters()
    .AddRemoteAppClient(options =>
    {
        options.RemoteAppUrl = new(builder.Configuration["ReverseProxy:Clusters:fallbackCluster:Destinations:fallbackApp:Address"]);
        options.ApiKey = builder.Configuration["RemoteAppApiKey"];
    })
    .AddAuthenticationClient(true);

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.UseSystemWebAdapters();

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

app.Run();