How to create ASP.NET Core host and run a request to it in the same process

Question

How can I host ASP.NET Core web application and run requests against it? I tried this but apparently Thread.Sleep(1000); is not a way to go.

var builder = WebApplication.CreateBuilder();
builder.Services.AddControllers();

var app = builder.Build();

app.Urls.Add(BaseAddress);
app.UseRouting();

app.MapControllers().AddApplicationPart(assemblyUnderTest);

Task.Run(() => app.Run());

Thread.Sleep(1000); // better solution needed.

var client = new HttpClient();
var response = client.GetAsync(BaseAddress + "/subpath/key").Result;
Console.WriteLine(response);
Console.WriteLine(response.Content.ReadAsStringAsync().Result);

Answer 1

As I've indicated in the comments section there is a hook called ApplicationStarted which is exposed through the IHostApplicationLifetime. This hook is a CancellationToken so, you can use the Register function to execute a custom code when it signals. Unfortunately it does not support asynchronous code.

Here is a working example how to issue a request against the application after it has been started:

using Microsoft.AspNetCore.Hosting.Server;
using Microsoft.AspNetCore.Hosting.Server.Features;

var builder = WebApplication.CreateBuilder();
var app = builder.Build();
app.MapGet("/test", () => "Test");

Task.Run(() => app.Run());

IHostApplicationLifetime lifetime = app.Lifetime;
lifetime.ApplicationStarted.Register(() =>
{
    var server = app.Services.GetService<IServer>();
    var addressesFeature = server?.Features.Get<IServerAddressesFeature>();
    var baseAddress = addressesFeature?.Addresses.FirstOrDefault(); 
    
    var client = new HttpClient();
    var response = client.GetAsync($"{baseAddress}/test").Result;
    Console.WriteLine(response.Content.ReadAsStringAsync().Result); //Test
});

Console.ReadLine();

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Here is a working dotnet fiddle. Please note the This is only required in dotnet fiddle comment.