Dotnet Core Multiple Startup Classes with In-Process Hosting

Question

I have a dotnet core v.2.1 application that utilizes the "startup-class-by-environment-name-convention" to use different Startup classes for different environment, e.g. development, staging and production. The Program.Main.CreateWebHost method looks similar to this:

public static IWebHostBuilder CreateWebHostBuilder(string[] args)
{
    var startupAssembly = Assembly.GetExecutingAssembly();
    var webHostBuilder = WebHost.CreateDefaultBuilder(args)
                                .UseStartup(startupAssembly.FullName);
    return webHostBuilder;
}

However, after upgrading to dotnet core v.2.2 (and the startup-switching still works great) I wanted to try out the in-process hosting capabilities. When switching to the in-process hosting model, and running locally with Visual Studio 2017 updated and IIS Express, I get this error running the application:

HTTP Error 500.30 - ANCM In-Process Start Failure

Common causes of this issue:

• The application failed to start
• The application started but then stopped
• The application started but threw an exception during startup

Troubleshooting steps:

• Check the system event log for error messages
• Enable logging the application process' stdout messages
• Attach a debugger to the application process and inspect

For more information visit: https://go.microsoft.com/fwlink/?LinkID=2028265

I checked all the logs, and all I could find was this:

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="IIS Express AspNetCore Module V2" /> 
    <EventID Qualifiers="0">1007</EventID> 
    <Level>2</Level> 
    <Task>0</Task> 
    <Keywords>0x80000000000000</Keywords> 
    <TimeCreated SystemTime="2018-12-14T10:37:48.327935100Z" /> 
    <EventRecordID>3693</EventRecordID> 
    <Channel>Application</Channel> 
    <Computer>[whatever]</Computer> 
    <Security /> 
  </System>
  <EventData>
    <Data>Application '/LM/W3SVC/2/ROOT' with physical root '[whatever again]' failed to load clr and managed application. CLR worker thread exited prematurely</Data> 
    <Data>Process Id: 29836.</Data> 
    <Data>File Version: 12.2.18316.0. Description: IIS ASP.NET Core Module V2 Request Handler. Commit: ce8cf65589734f82b0536c543aba5bd60d0a5a98</Data> 
  </EventData>
</Event>

I read all the dotnet core in-hosting migrate 2.1 -> 2.2 whatever MSDN articles I could find, and tried a bunch of different set-ups, but could find no solution apart from using the default:

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
           .UseStartup<Startup>();

... Which will not do - I want to use the startup-switching together with the in-process hosting. Does anyone know how to achieve this, or have any suggestions on how to proceed with the troubleshooting?

EDIT: I got the answer I needed from @cilerler. For the sake of completeness, here's what was going on in my case:

The loading of my custom configuration files failed because this process depended on a call to Directory.GetCurrentDirectory(), the result of which changes when switching to in-process hosting. Here's my original code for that part (shortened for brevity):

var basePath = $"{Directory.GetCurrentDirectory()}\\ConfigurationFiles";
builder.SetBasePath(basePath);

builder.AddJsonFile("some.config.json", false, true);
builder.AddJsonFile($"some.config.{context.HostingEnvironment.EnvironmentName}.json", true, true);

The crucial part is - again - the call to GetCurrentDirectory(), so, to fix the issue, I changed the above as per the recommendation in the accepted answer, to:

var currentDirectory = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
var basePath = $"{currentDirectory}\\ConfigurationFiles";
builder.SetBasePath(basePath);

For further details, see the accepted answer ;)

Answer 1

According to aspnet-core-module article it says

GetCurrentDirectory returns the worker directory of the process started by IIS rather than the app's directory (for example, C:\Windows\System32\inetsrv for w3wp.exe).

which means config loader will not be able to find appsettings.* files, or any other files such as custom config files, that depend on a GetCurrentDirectory call. In order to solve it in your Program.cs right after public static void Main(string[] args) { add the following line

Directory.SetCurrentDirectory(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location));

Also, in project file (e.g. MyProject.csproj) make sure that you have the following lines and appsettings.* exists in output folder.

<ItemGroup>
  <Content Update="appsettings.json">
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
  </Content>
  <Content Update="appsettings.Development.json">
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
  </Content>
  <Content Update="appsettings.Production.json">
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
  </Content>
</ItemGroup>