PowerShell App.Config

Question

Has anyone worked out how to get PowerShell to use app.config files? I have a couple of .NET DLL's I'd like to use in one of my scripts but they expect their own config sections to be present in app.config/web.config.

Answer 1

Cross-referencing with this thread, which helped me with the same question: Subsonic Access To App.Config Connection Strings From Referenced DLL in Powershell Script

I added the following to my script, before invoking the DLL that needs config settings, where $configpath is the location of the file I want to load:

[appdomain]::CurrentDomain.SetData("APP_CONFIG_FILE", $configpath)
Add-Type -AssemblyName System.Configuration

See this post to ensure the configuration file specified is applied to the running context.

Answer 2

I'm guessing that the settings would have to be in powershell.exe.config in the powershell directory, but that seems to be a bad way of doing things.

You can use ConfigurationManager.OpenMappedExeConfiguration to open a configuration file based on the executing DLL name, rather than the application exe, but this would obviously require changes to the DLLs.

Answer 3

Attempting a new answer to an old question.

I think the modern answer would be: don't do that. PowerShell is a shell. The normal way of passing information between parts of the shell are shell variables. For powershell that would look like:

$global:MyComponent_MySetting = '12'
# i.e. 
$PSDefaultParameterValues
$ErrorActionPreference

If settings is expected to be inherited across processes boundaries the convention is to use environment variables. I extend this to settings that cross C# / PowerShell boundary. A couple of examples:

$env:PATH
$env:PSModulePath

If you think this is an anti-pattern for .NET you might want to reconsider. This is the norm for PAAS hosted apps, and is going to be the new default for ASP.NET running on server-optimized CLR (ASP.NET v5).

See https://github.com/JabbR/JabbRv2/blob/dev/src/JabbR/Startup.cs#L21
Note: at time of writing I'm linking to .AddEnvironmentVariables()

I've revisited this question a few times, including asking it myself. I wanted to put a stake in the ground to say PowerShell stuff doesn't work well with <appSettings>. IMO it is much better to embrace the shell aspect of PS over the .NET aspect in this regards.

If you need complex configuration take a JSON string. POSH v3+ has ConvertFrom-JSON built-in. If everything in your process uses the same complex configuration put it in a .json file and point to that file from an environment variable.

If a single file doesn't suffice there are well established solutions like the PATH pattern, GIT .gitignore resolution, or ASP.NET web.config resolution (which I won't repeat here).