An asp.net core web api application, using "UseWindowsService", reports an error “System.NotSupportedException: The content root changed. Changing the host configuration is not supported ” when starting the service

[quan0zhou]

• System

  • Provider

  [ Name] .NET Runtime

  • EventID 1026

  [ Qualifiers] 0

  Version 0

  Level 2

  Task 0

  Opcode 0

  Keywords 0x80000000000000

  • TimeCreated

  [ SystemTime] 2021-09-26T05:59:39.0432975Z

  EventRecordID 14008

  Correlation

  • Execution

  [ ProcessID] 0
  [ ThreadID] 0

  Channel Application

  Computer USER-20210710BJ

  Security

• EventData

  Application: ZhaoyangParking.exe CoreCLR Version: 6.0.21.45113 .NET Version: 6.0.0-rc.1.21451.13 Description: The process was terminated due to an unhandled exception. Exception Info: System.NotSupportedException: The content root changed. Changing the host configuration is not supported at Microsoft.AspNetCore.Builder.ConfigureHostBuilder.ConfigureHostConfiguration(Action1 configureDelegate) at Microsoft.Extensions.Hosting.HostingHostBuilderExtensions.UseContentRoot(IHostBuilder , String ) at Microsoft.Extensions.Hosting.WindowsServiceLifetimeHostBuilderExtensions.UseWindowsService(IHostBuilder hostBuilder, Action1 configure) at Microsoft.Extensions.Hosting.WindowsServiceLifetimeHostBuilderExtensions.UseWindowsService(IHostBuilder hostBuilder) at Program.

  $(String[] args) in E:\Learn\ZhaoyangParking\ZhaoyangParking\Program.cs:line 20

But There is nothing wrong with the program in .NET Version: 6.0.0-preview.7.21377.19

---

Document Details

⚠ Do not edit this section. It is required for docs.microsoft.com ➟ GitHub issue linking.

• ID: b0bd8cb8-7e28-8c4d-a550-3aea8f3ab4dd
• Version Independent ID: 4b60d24e-ef05-15e5-10b4-483094081bf3
• Content: Host ASP.NET Core in a Windows Service
• Content Source: aspnetcore/host-and-deploy/windows-service.md
• Product: aspnet-core
• Technology: aspnetcore-hostdeploy
• GitHub Login: @Rick-Anderson
• Microsoft Alias: riande

[quan0zhou]

Find the relevant code through the source code

After decompiling the source code from Microsoft.Extensions.Hosting.WindowsServices.dll, I found the solution

[quan0zhou]

var builder = WebApplication.CreateBuilder(args);

builder.Configuration.AddJsonFile(Path.Combine(AppContext.BaseDirectory, "appsettings.json"));

builder.Host
       //.UseWindowsService()//error: The content root changed. Changing the host configuration is not supported
       .ConfigureLogging(logging =>
       {
           logging.AddEventLog();

       }).ConfigureServices((hostContext, services)=>
       {
           services.AddSingleton<IHostLifetime, WindowsServiceLifetime>();
           services.Configure<EventLogSettings>(settings=>
           {
               if (string.IsNullOrEmpty(settings.SourceName))
               {
                   settings.SourceName = hostContext.HostingEnvironment.ApplicationName;
               }
           });
           services.AddHostedService<xxxxService>();

       });

[davidfowl]

Yes this is unfortunate and one of the gotchas listed here (https://gist.github.com/davidfowl/0e0372c3c1d895c3ce195ba983b1e03d#differences-in-the-hosting-model).

@quan0zhou Can you tell me what the content root is when you host as a windows service?

Also can you try this workaround:

using Microsoft.Extensions.Hosting.WindowsServices;

var options = new WebApplicationOptions
{
    Args = args,
    ContentRootPath = WindowsServiceHelpers.IsWindowsService() ? AppContext.BaseDirectory : default
};

var builder = WebApplication.CreateBuilder(options);

builder.Host.UseWindowsService();

[davidfowl]

@quan0zhou Can you tell me what the content root is when you host as a windows service?

Don't worry, I have a repro with this. I think there might be an easy fix that makes this work by default.

[davidfowl]

@halter73 @Tratcher This is where we set the default content root to be the CWD (called from here), which is why the windows service logic needs to change it back to AppContext.BaseDirectory. If we could be a bit more clever about this default then it wouldn't require any explicit workarounds (for this case).

cc @eerhardt

[davidfowl]

I have another idea that doesn't require changing to much code. We update the documentation to pass the correct content root via command line args when creating the service:

sc config MyWebAppServiceTest binPath= "$pwd\WebApplication560.exe --contentRoot $pwd\"

We should update the docs to reflect this.

We also need to make a change to the host so that the content root comparison is on normalized paths. If you specify $pwd without the trailing slash, it fails because we compare the directories and it has to be an exact match today.

[davidfowl]

This should be a CTI scenario that we cover.

cc @captainsafia

[quan0zhou]

是的， 这是不幸的， 这里列出的哥查斯之一（https://gist.github.com/davidfowl/0e0372c3c1d895c3ce195ba983b1e03d#differences-in-the-hosting-model）。

@quan0zhou当您作为窗口服务托管时，你能告诉我内容根是什么吗？

您也可以尝试此解决方法：

using Microsoft.Extensions.Hosting.WindowsServices;

var options = new WebApplicationOptions
{
    Args = args,
    ContentRootPath = WindowsServiceHelpers.IsWindowsService() ? AppContext.BaseDirectory : default
};

var builder = WebApplication.CreateBuilder(options);

builder.Host.UseWindowsService();

@davidfowl This is a great solution, thanks!

[davidfowl]

We need to update the windows service hosting document https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/windows-service?view=aspnetcore-5.0&tabs=visual-studio to mention that the service should be created passing the --contentRoot argument.

We might want to do the same here for good measure:

https://docs.microsoft.com/en-us/dotnet/core/extensions/windows-service#create-the-windows-service cc @IEvangelist

[IEvangelist]

We need to update the windows service hosting document https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/windows-service?view=aspnetcore-5.0&tabs=visual-studio to mention that the service should be created passing the --contentRoot argument.

We might want to do the same here for good measure:

https://docs.microsoft.com/en-us/dotnet/core/extensions/windows-service#create-the-windows-service cc @IEvangelist

Thanks for the heads up @davidfowl - see dotnet/docs#26274

[Rick-Anderson]

See Create the Windows Service

https://github.com/dotnet/docs/pull/26372/files:

Tip

If you need to change the content root of the host configuration, you can pass it as a command-line argument when specifying the binpath:

sc.exe create "Svc Name" binpath="C:\Path\To\App.exe --contentRoot C:\Other\Path"

[DapperDeer]

Hey there,

I am trying to create my service with the new --contentRoot argument but am experiencing this issue where the argument isn't accepting a space character:

sc.exe create Diagnostics binPath="C:\Program Files\Diagnostics\Diagnostics.exe --contentRoot C:\Program Files\Diagnostics"

Application: Diagnostics.exe
CoreCLR Version: 6.0.322.12309
.NET Version: 6.0.3
Description: The process was terminated due to an unhandled exception.
Exception Info: System.IO.DirectoryNotFoundException: C:\Program\

I've tried putting the path in single quotes ala --contentRoot 'C:\Program Files\Diagnostics' but no luck on that either - in fact, it's strangely mixing my working directory and part of the given content root?

Application: Diagnostics.exe
CoreCLR Version: 6.0.322.12309
.NET Version: 6.0.3
Description: The process was terminated due to an unhandled exception.
Exception Info: System.IO.DirectoryNotFoundException: C:\Program Files\Diagnostics\'C:\Program\

Entirely possible I'm missing a simple solution, but please advise nonetheless.

Thanks.

Edit: I was able to work around this by being in the directory I waned the Content Root to be and setting it as ./, but this may still be something to look into?

[davidfowl]

Yes, we plan to make this a bit more seamless so nothing has to be changed by default.

[josdan018]

I am trying to create my service with the new --contentRoot argument but am experiencing this issue where the argument isn't accepting a space character:

sc.exe create Diagnostics binPath="C:\Program Files\Diagnostics\Diagnostics.exe --contentRoot C:\Program Files\Diagnostics"

Application: Diagnostics.exe
CoreCLR Version: 6.0.322.12309
.NET Version: 6.0.3
Description: The process was terminated due to an unhandled exception.
Exception Info: System.IO.DirectoryNotFoundException: C:\Program\

@DapperDeer .exe path should be quoted ref

[SimoneBWS]

In my case it works with:
sc create MyApp binpath="C:\Program Files\Contoso\MyApp\bin\MyApp.exe --contentRoot C:\Program Files\Contoso\MyApp\bin\"

[tbayart]

2 years later, we still face the same issue
@davidfowl can you tell me if there is a reason to set the ContentRootPath only when the application run as a Windows service ?

ContentRootPath = WindowsServiceHelpers.IsWindowsService() ? AppContext.BaseDirectory : default

also if this is still considered as a workaround, is there a cleaner way to start a Krestrel as a Windows service ?

[davidfowl]

What version of .NET are you running?

[tbayart]

net6.0 LTS

[davidfowl]

It's fixed in .NET 7+

[tbayart]

Thanks for the update, i will check that with incoming net8.0 upgrade

[mateuszPATeam]

Apologies for digging up an old thread, but I'm unable to set the content root path, no matter what I do. My application is self-contained, single executable, and I want to host it as a Windows Service. I applied the above snippet and tried to create the service with --contentRoot, but it just doesn't do anything and my Content Root is always pointing to a folder in Windows. The target framework is .NET 6. Any ideas how I can fix it?

[tbayart]

@davidfowl workaround solved the issue on my side for my .net 6 version
#23387 (comment)

if it's not your case, try to reproduce your issue with minimal code and post it here so we can help you solve your problem