.NET Core 6 Found multiple publish output files with the same relative path

Question

I'm running into a relatively new issue on .NET Core 6 where when publishing with Web Deploy via Visual Studio 2022. I'm receiving the following error:

Error Found multiple publish output files with the same relative path: C:\Work\MySolution\A\appsettings.json, C:\Work\MySolution\B\appsettings.json, C:\Work\MySolution\A\appsettings.Staging.json, C:\Work\MySolution\B\appsettings.Staging.json, , C:\Work\MySolution\A\appsettings.Development.json, C:\Work\MySolution\B\appsettings.Development.json

There is no issues when building, just publishing.

I have two ASP.NET Core 6 projects. Project "A" references project "B" (I know B should really be a class library, but go with me).

I am aware that this is expected functionality in .NET Core 6 (https://docs.microsoft.com/en-us/dotnet/core/compatibility/sdk/6.0/duplicate-files-in-output). However, I cannot seem to tell project "A" to ignore project "B" appsettings files. I am aware of the ErrorOnDuplicatePublishOutputFiles property I can set, but I'm trying to strictly tell it not to include those files.

Here's some examples of items that I have tried, but does not work.

Example 1: Tried typical content update approach (supposedly does not work after VS 15.3). Also tried with absolute paths.

A.csproj

...


  
    all
  

  
    
  
  


...

Example 2: Tried typical content remove approach. Also tried with absolute paths.

A.csproj

Example 3: I tried using the GeneratePathProperty path to make sure it was directly ignoring project B's files.

A.csproj

...


  
    all
  

  
    
  
  


...

Example 4: Modified pubxml to ignore specific files. Tried with absolute paths too.

A.pubxml

...

..\B\appsettings.json;..\B\appsettings.Staging.json;... 

...

Example 5: Modified pubxml file to explicity ignore project B files. Tried absolute paths as well.

A.pubxml

...


  
    Never
  
  
    Never
  
  
    Never
  
  
    Never
  


...

I've tried various other combos, but none of it seems to work...

Windows 10
Visual Studio 2022 (latest)
.NET Core 6

user_420400 · Answer

I ran into this problem upgrading .NET 5 web services to .NET 6. As the link you provided points out, this is by design now. I fixed it by renaming the appsettings.json file in both projects by prepending the assembly name, and then reconfiguring the configuration (yes, that's a thing) as follows:

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.ConfigureAppConfiguration((context, configBuilder) =>
            {
                string assemblyName = Assembly.GetExecutingAssembly().GetName().Name;
                string envName = context.HostingEnvironment.EnvironmentName;
                configBuilder.Sources.Clear();
                configBuilder.AddJsonFile($"{assemblyName}.appsettings.json", optional: false, reloadOnChange: true);
                configBuilder.AddJsonFile($"{assemblyName}.appsettings.{envName}.json", optional: true, reloadOnChange: true);
            });
            webBuilder.UseStartup();

As you can see, our code is still ".NET 5-style" at this point.

user_11753128 · Answer

I ran into this issue with a web application that had a Razor Class Library. The Culprit file was LIBMAN.JSON.

Change the properties of the file to:

Build Action: NONE

Copy to Output Directory: DO NOT COPY

Other files that are used for tooling only could possibly be changes the same way.

.NET Core 6 Found multiple publish output files with the same relative path

2 Answers