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ContentRootPath for apps launched by Windows Shell

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The IHostEnvironment.ContentRootPath property represents the default directory where appsettings.json and other content files are loaded in a hosted application, including ASP.NET apps. This property's value defaults to Environment.CurrentDirectory, which is the current working directory of the application. This behavior allows the same app to be executed under different working directories and use the content from each directory.

When a Windows process (either application or service) is launched without specifying a working directory, the working directory of the process that created it is used. The working directory of Windows Shell or services.exe is %windir%\system32 (or the System special folder). When either of those processes launches a hosted app, the ContentRootPath property is set to %windir%\system32.

This behavior is confusing and causes hosted applications to fail, because the application tries to load files from the %windir%\system32 directory, but it doesn't exist. For example, the appsettings.json file is not found at run time and the settings aren't applied.

Starting with .NET 7, when a hosted application is launched with the current directory set to the System special folder, it defaults the ContentRootPath property to AppContext.BaseDirectory.

Version introduced

.NET 7

Previous behavior

Host.CreateDefaultBuilder defaulted the ContentRootPath property to Environment.CurrentDirectory regardless of the value of the current directory.

New behavior

Host.CreateDefaultBuilder no longer defaults the ContentRootPath property to the current directory if it's the System special folder on Windows. Instead, the base directory of the application is used.

Type of breaking change

This change can affect binary compatibility.

Reason for change

App developers weren't expecting ContentRootPath to be C:\Windows\system32 when their application was launched by Windows in certain cases (for example, when the app was packaged as an MSIX or started from the Start Menu). In these cases, it's better to default the ContentRootPath property to the base directory of the application.

If you want to use the previous behavior, you can set the ContentRootPath property explicitly when creating the IHostBuilder:

Host
    .CreateDefaultBuilder()
    .UseContentRoot(Environment.CurrentDirectory)
    ....

Affected APIs