Display startup errors in ANCM

[pakrym]

No description provided.

[Tratcher]

👀

[jkotalik]

I'll be taking this over eventually, but we still need some downstream dependencies.

[jkotalik]

I have a prototype of this using replicating the hosting exception page. Currently looks like:

As @pakrym mentioned, this unfortunately brings in some dependencies that will be present in every inproc app. Here are the usings I have for the startup hook.

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Text.Encodings.Web;
using Microsoft.AspNetCore.Server.IIS;
using Microsoft.Extensions.FileProviders;
using Microsoft.Extensions.Primitives;
using Microsoft.Extensions.StackTrace.Sources;

[Tratcher]

Hosting already has all of those dependencies, no? You wouldn't be adding anything new.

[jkotalik]

Blocked on dotnet/coreclr#23178 and https://github.com/dotnet/coreclr/issues/23343

[jkotalik]

This is now working. Probably a bit of cleanup around the edges (like using host properties rather than environment variables), but overall it looks good.

Here is what the exception page looks like:

And showing the .NET Runtime event log:

[jkotalik]

There are two scenarios here. One which loads from a resource file (page number passed in) and the other is passed in via the startup hook. I have a 3rd constructor which takes both.

[jkotalik]

This is mostly taken from https://github.com/aspnet/AspNetCore/blob/4e44025a52e4b73aa17e09a8041b0e166e0c5ce0/src/Hosting/Hosting/src/Internal/WebHost.cs#L245

[jkotalik]

I'm going to try verifying this change E2E ASAP. I'm confident in the change, but I would like to make sure this works as part of the SDK.