Loading a configuration file in a separate appdomain

I lost some time today investigating how to load an app.config for a separate domain. My first attempt looked like this:

	<?xml version="1.0" encoding="utf-8" ?>
	<configuration>
	<startup>
	<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />
	</startup>
	<appSettings>
	<add key="Hello" value="Hello World!"/>
	</appSettings>
	</configuration>

view raw OtherConsoleApp.exe.config hosted with ❤ by GitHub

	class Program
	{
	static void Main(string[] args)
	{
	Console.WriteLine(ConfigurationManager.AppSettings["Hello"]);
	}
	}

view raw OtherConsoleApp.Program.cs hosted with ❤ by GitHub

	var appDomainSetup = new AppDomainSetup();
	var configPath= Path.Combine(Environment.CurrentDirectory, "OtherConsoleApp.exe.config");
	appDomainSetup.ConfigurationFile = configPath;
	var domain=AppDomain.CreateDomain("OtherConsoleApp",null,appDomainSetup);
	domain.ExecuteAssembly("OtherConsoleApp.exe");
	AppDomain.Unload(domain);

view raw program.cs hosted with ❤ by GitHub

However the call to ConfigurationManager.AppSettings always returned null. I first thought that I did something wrong when configuring the AppDomainSetup.

I first tried to replace the AppDomainSetup configuration to explicitly load the config settings:

	var appDomainSetup = new AppDomainSetup();
	var configPath= Path.Combine(Environment.CurrentDirectory, "OtherConsoleApp.exe.config");
	appDomainSetup.SetConfigurationBytes(File.ReadAllBytes(configPath));

view raw Program.cs hosted with ❤ by GitHub

But this did not solve the issue. In the end I discovered that it was the ConfigurationManager.AppSettings that was causing the issue. When I replaced it with the code below, it started to work!

	class Program
	{
	static void Main(string[] args)
	{
	var config=ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
	Console.WriteLine(config.AppSettings.Settings["Hello"].Value);
	}
	}

view raw OtherConsoleApp.Program.cs hosted with ❤ by GitHub