Minimum code needed to run/experiment with functionality from an AspNetCore project

AspNetCore LinqPad Playground.cs

/*
References (F4 - Additional References - Add...)
~~~~~~~~~~~~~~~~~~~
<Your AspNetCore site assembly>
* Check Reference ASP.NET Core

Using (F4 - Additional Namespace Imports)
~~~~~~~~~~~~~~~~~~~
Microsoft.AspNetCore.Hosting
Microsoft.Extensions.Configuration
Microsoft.Extensions.DependencyInjection
System.Threading.Tasks
*/

#region Boilderplate for AspNetCore playground in LinqPad
public IServiceScope serviceScope;

void SetupPlayground()
{
	//HibernatingRhinos.Profiler.Appender.NHibernate.NHibernateProfiler.Initialize();//Setup NHibernate Profiling
	
	var sw = Stopwatch.StartNew(); //Just for tracking how long Setup() takes
	$"Setting up playground: 0 seconds".Dump();
	
	//an IWebHostEnvironment for Linqpad
	var hostingEnvironment = new LinqPadHostingEnvironment(@"C:\Users\Nick\source\repos\WebApplication9");
	//Initialize and setup ConfigurationManager
	var config = new Microsoft.Extensions.Configuration.ConfigurationManager();
	config.SetBasePath(hostingEnvironment.ContentRootPath)
		.AddJsonFile("appsettings.json")
		.AddJsonFile(string.Format("appsettings.{0}.json", (object)hostingEnvironment.EnvironmentName), true, true);
	config.AddUserSecrets("dfe1bb4f-1634-453b-b602-a68d00741aba")
		.AddInMemoryCollection([new KeyValuePair<string, string>("Environment", "Development")])
		.Build();

	//Dependency Injection
	var services = new ServiceCollection();
	services.AddSingleton<Microsoft.AspNetCore.Hosting.IWebHostEnvironment>(hostingEnvironment);
	services.AddSingleton<Microsoft.AspNetCore.Hosting.IHostingEnvironment>(hostingEnvironment); //Only if you need it
		
	//public static void SetupConfiguration(ConfigurationManager configuration)
	Program.SetupConfiguration(config);
	$"Project Configuration ready: {sw.Elapsed.TotalSeconds} seconds".Dump();
	//public static void ConfigureServices(IServiceCollection services, ConfigurationManager configuration, IHostEnvironment environment)
	Program.ConfigureServices(services, config, hostingEnvironment);
	$"Project Services ready: {sw.Elapsed.TotalSeconds} seconds".Dump();

	var serviceProvider = services.BuildServiceProvider();
	serviceScope = serviceProvider.CreateScope();
	$"Provider & scope created: {sw.Elapsed.TotalSeconds} seconds".Dump();
	
	sw.Stop();
	$"Playground setup completed Startup Completed: {sw.Elapsed.TotalSeconds} seconds".Dump();
}

public class LinqPadHostingEnvironment : IWebHostEnvironment, Microsoft.Extensions.Hosting.IHostingEnvironment, Microsoft.AspNetCore.Hosting.IHostingEnvironment
{
	public LinqPadHostingEnvironment(string aspNetCoreProjectDirectory)
	{
		EnvironmentName = "Development";
		ApplicationName = "LinqPad";
		ContentRootPath = aspNetCoreProjectDirectory;
		WebRootPath = System.IO.Path.Combine(aspNetCoreProjectDirectory, "wwwroot");
	}
	public string EnvironmentName { get; set; }
	public string ApplicationName { get; set; }
	public string WebRootPath { get; set; }
	public Microsoft.Extensions.FileProviders.IFileProvider WebRootFileProvider { get; set; }
	public string ContentRootPath { get; set; }
	public Microsoft.Extensions.FileProviders.IFileProvider ContentRootFileProvider { get; set; }
}
#endregion

void Main()
{
	try
	{
		/* Useful for forcing a new process every time */
		//Util.NewProcess = true;

		//Sets up playground for use
		SetupPlayground();
		//Optionally begin transaction here
		
		//DO STUFF HERE





		//optionally commit transaction
	}
	catch (Exception ex)
	{
		ex.Dump();
		//optionally rollback transaction
	}
	finally
	{
		serviceScope?.Dispose();
	}
}

Program.cs

//While your default implimentation will likely have this as a minimal Program class, we need to split it up and ilsolate the setup of Confiration and Services so that they can be used from LinqPad
public class Program
{
    public static void Main(string[] args)
    {
        var builder = WebApplication.CreateBuilder(args);

        //1. Initialize Configuration
        SetupConfiguration(builder.Configuration);

        //2. Configure the services needed
        ConfigureServices(builder.Services, builder.Configuration, builder.Environment);

        //3. Configure the middleware pipeline
        var app = builder.Build();
        ConfigureMiddleware(app);

        //RUN!
        app.Run();
    }

    public static void SetupConfiguration(ConfigurationManager configuration)
    {
        //Setup & add additional configuration sources
    }

    /// <param name="configuration">So that we can add Options to the services based off of confiration sections</param>
    /// <param name="environment">So that we can differ our services setup based on IsDevelopment() </param>
    public static void ConfigureServices(IServiceCollection services, ConfigurationManager configuration, IHostEnvironment environment)
    {
        //Add services
        services.AddControllersWithViews();
    }

    private static void ConfigureMiddleware(WebApplication app) //Made private because we don't access this method externally when running in LinqPad
    {
        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.UseAuthorization();

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

Updated with what I currently use with .NET Core 8