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How to acced to my app.config from c# interactive?

I initialized the interactive element with the project from the context menu of my project.
I am testing a function in C# interactive that needs to read my app.config file to get a connectionstring.
I got the next error:
No connection string named 'ccnName' could be found in the application config file.
When I use the next code, i get a null value. I suppose it is because it is not reading the app.config of my project.
ConfigurationManager.ConnectionStrings["cnnName"]
It is the only connectionstring that the default app.config has:
[data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true]
In this post from 2012 with the same topic, one engineer involved in this project said that this option was not available. I hope it is available now in 2018
So, nowadays how can i load the app.config that i want?

"Constructor" was the magic word. This may not help in your case since you've found a solution, but it might be helpful for others in the same situation.
If you inject a System.Configuration.Configuration object into the class, you don't have to rely on ConfigurationManager's static properties.
public class LibraryClass
{
private Configuration _configuration;
public LibraryClass(Configuration configuration)
{
_configuration = configuration ?? throw new ArgumentNullException(nameof(configuration));
}
public void FunctionUnderTest()
{
string connectionString = _configuration.ConnectionStrings.ConnectionStrings["cnnName"].ConnectionString;
// Connect to the database as you normally would.
}
}
In a console/GUI application and unit tests, load it like this to use {anything}.config:
Configuration configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
// Register 'configuration' as a singleton using the container of your choice.
In a web application, load it like this to use web.config:
Configuration configuration = WebConfigurationManager.OpenWebConfiguration("~/Web.config");
// Register 'configuration' as a singleton using the container of your choice.
To use it in C# Interactive, load it using the first method and provide the dependency to the class directly:
#r "System.Configuration"
Configuration configuration = ConfigurationManager.OpenMappedExeConfiguration(
new ExeconfigurationFileMap() { ExeConfigFilename = #"path\to\Arbitrary.config" },
ConfigurationUserLevel.None);
var lib = new LibraryClass(configuration);
lib.FunctionUnderTest();
Note that the section properties are an extra layer deep compared to what you would normally expect.
I think it has something to do with how ConfigurationManager's static properties work with the Configuration instance.

Logger does not work in newly created AppDomain

In my Application I use Common.Logging library in order to abstract logging functionality. In startup assembly it was configured (in app.config file) to work against Log4Net library. There are established some Appenders: ConsoleAppender, RollingFileAppender, TraceAppender. Everything works fine in the single AppDomain. However I have found that logging does not work in the newly created AppDomain. i.e:
Logger.Info( "Logging works here" ); // Logging works here
var appDomain = AppDomain.CreateDomain(
"AppDomain." + componentHost.FullName,
AppDomain.CurrentDomain.Evidence,
AppDomain.CurrentDomain.SetupInformation );
var proxy = (IComponentHost) appDomain.CreateInstanceAndUnwrap(
componentHost.Assembly.FullName,
componentHost.FullName,
false,
BindingFlags.Default,
null,
new object[] { },
null,
null );
proxy.Init(); // Logging does not work in Init() method stack
I'm trying to find a solution, both using app.config configuration as well as Common.Logging API (i.e LogManager.Reset() method), but it doesn't solve a problem.
How can I force Common.Logging / Log4Net to work properly in newly created AppDomain? Please for help.

I have a similar issue with log4net. I used XmlConfigurator.Configure() without parameters that uses Assembly.GetCallingAssembly() to get configuration file. I replaced it with:
var configFile = new FileInfo(AppDomain.CurrentDomain.SetupInformation.ConfigurationFile);
if (!configFile.Exists)
throw new Exception($"Failed to find configuration file '{configFile.FullName}'");
XmlConfigurator.Configure(configFile);

From the code you show, it looks like you're not providing a configuration file for your app domain. It's been a few years since I've done this, but if I recall correctly, the configuration file for a new app domain is empty by default.
Here's an example of how to use the AppDomainSetup class:
AppDomainSetup ads = new AppDomainSetup();
ads.SetConfigurationBytes( Encoding.UTF8.GetBytes(
#"<configuration>
<system.data>
<DbProviderFactories>
<remove invariant="System.Data.SqlServerCe.3.5"></remove>
</DbProviderFactories>
</configuration>" ) );
(Credit to Tom Overton for the code sample.)
See http://social.msdn.microsoft.com/Forums/vstudio/en-US/a23ff0ad-8a4c-4aaf-8281-dcc7e840f8a5/assigning-appconfig-to-appdomain?forum=clr for his explanation of this issue.

exePath must be specified when not running inside a stand alone exe

When i am using a web application, the line of code below
Configuration objConfig =
ConfigurationManager.OpenExeConfiguration( ConfigurationUserLevel.None);
in class library are giving this error:
"exePath must be specified when not running inside a stand alone exe."
Previously a console application was being used, and the code could access the app.config. I tried using the System.Web.Configuration in class library but the dll was not present in the .Net tab for "Add reference".
Kindly help :)

You need to use a different configuration manager in a web context. The following code
block shows an example of how to deal with this:
System.Configuration.Configuration configuration = null;
if (System.Web.HttpContext.Current != null)
{
configuration =
System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration("~");
}
else
{
configuration =
ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
}

I'm not sure what you're doing; but at first glance it looks like you're trying to use code written for a WinForms application in a web environment. This almost certainly will not work, since your web app won't have the permissions you need.
Try looking up how to do this in a web environment (since you seem to be dealing with config files, try searching on WEB.CONFIG to start)

I tried to use the answer from #shane but ended up with the same exception using Hangfire. This code worked for me though:
System.Configuration.Configuration configFile = null;
if (System.Web.HttpContext.Current != null)
{
configFile =
System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration("~");
}
else
{
System.Configuration.ExeConfigurationFileMap map = new ExeConfigurationFileMap { ExeConfigFilename = $"{System.AppDomain.CurrentDomain.BaseDirectory}Web.Config" };
configFile = ConfigurationManager.OpenMappedExeConfiguration(map, ConfigurationUserLevel.None);
}
Note that editing Web.config will cause the application pool to restart!

Unable to load executing assembly into new AppDomain, FileNotFoundException

I am trying to host a text template class proxy inside a new AppDomain.
I have some old scripting code that does something similar, that contains this working code:
_ScriptAppDomain = AppDomain.CreateDomain(scriptDomainFriendlyName);
_ScriptProxy = (IScriptEngineProxy)_ScriptAppDomain.CreateInstanceAndUnwrap(
Assembly.GetExecutingAssembly().FullName,
"LVK.Scripting.ScriptEngineProxy");
However, when I try this with my new class, with the following
_TemplateDomain = AppDomain.CreateDomain(templateDomainFriendlyName);
_TemplateProxy = (ITemplateProxy)_TemplateDomain.CreateInstanceAndUnwrap(
Assembly.GetExecutingAssembly().FullName,
"TextTemplate.TemplateProxy");
I just get "FileNotFoundException", with the following details:
Could not load file or assembly 'TextTemplate, Version=1.0.0.0, Culture=neutral, PublicKeyToken=bb70a2e62a722ace' or one of its dependencies. The system cannot find the file specified.
What am I missing?
Basically, I have a Template class in the TextTemplate namespace (and assembly), which tries to load a TemplateProxy class (descending from MarshalByRefObject) into the new appdomain, but it appears my main assembly is not loaded into this domain.
This works if I use the older code, but not with this new one, but I can't spot the difference.
Here's some more details:
Assembly is not registered with the GAC (neither was the old one, which works)
I have not overridden any AssemblyResolve event (neither did the old one, which works)
I'm not averse to handling the AssemblyResolve event, if that is what is needed. I just found it odd that my old code worked, and this didn't.

Assumying your assembly is in the same directory as your current application base, try specifying Application Base:
AppDomain.CreateDomain(templateDomainFriendlyName, null,
new AppDomainSetup
{
ApplicationBase = AppDomain.CurrentDomain.SetupInformation.ApplicationBase
});

If you don't know what you are doing, the best way to create a new domain is to copy all settings from the current one, like this:
var newDomain = AppDomain.CreateDomain("NAME",
AppDomain.CurrentDomain.Evidence,
AppDomain.CurrentDomain.SetupInformation);
I had similar issues, and making a copy resolved them for me

How do I specify the name of my application's App.config file in WPF?

This is very frustrating... I can set the Configuration File for a Windows Forms Application just fine. Consider this:
public static void Main(){
AppDomain.CurrentDomain.SetData("APP_CONFIG_FILE", #"SharedAppConfig.config");
//do other things
}
However, in a WPF application, this doesn't seem to work! If I set this value, the value of the AppDomain.CurrentDomain.SetupInformation.ConfigurationFile property is correct, but any calls to that configuration file while debugging yield no results. There are WCF configuration settings in an App.config that I need to share between application, so this is my proposed solution. Is it possible to dynamically set the location of my config file in WPF?
Help! Thanks!

You should be able to do something along the lines of:
using System.Configuration;
public class TryThis
{
Configuration config = ConfigurationManager.OpenExeConfiguration("C:\PathTo\app.exe");
public static void Main()
{
// Get something from the config to test.
string test = config.AppSettings.Settings["TestSetting"].Value;
// Set a value in the config file.
config.AppSettings.Settings["TestSetting"].Value = test;
// Save the changes to disk.
config.Save(ConfigurationSaveMode.Modified);
}
}
NOTE: This will attempt to open a file named app.exe.config at C:\PathTo. This also REQUIRES that a file exists at the same path with the name "app.exe". The "app.exe" file can just be an empty file though. For your case I'd almost make a shared "Config.dll" library that would handle the config file.
~md5sum~

Is this on the service side or the client side? If on the service side, it is often the case that the service is running in its own AppDomain, so that if you set AppDomain.CurrentDomain.SetData(...) it won't apply to the service configuration.
I'm not entirely sure how to get around this, but you should be able to control the service's configuration by implementing your own ServiceHost.