Where are config files for class libraries physically located?

Question

My guess is that this question will fall under the category of "duh", but, nevertheless, I'm confused.

When using config files in, for example, a Windows Forms Application, the config file can be found in C:\Program files\CompanyName\ProductName\Application.exe.config. However, with the class library I'm developing I do not see a "ClassLibrary.dll.config" file in the install folder after installing it (in tandem with another project) from Visual Studio. Even though I do not see the file anywhere, retrieving data from it works correctly. Plus, running the following code from a method within the class library returns the path you would expect: C:\Program files\CompanyName\ProductName\ClassLibrary.dll.config.

If someone could shed some light on what I'm missing here, that would be really awesome.

public static string MyMethod()
{
Assembly assem = Assembly.GetExecutingAssembly();
Configuration config = ConfigurationManager.OpenExeConfiguration(assem.Location);

return "The assembly location was: " + assem.Location + Environment.NewLine +
"The config file path was: " + config.FilePath;

// Gives me "C:\Program files\CompanyName\ProductName\ClassLibrary.dll.config"

}

Answer 1

Depends on the version of .NET. Prior to .NET 4.0, class libraries cannot use their own app.config files unless you do custom stuff to read the data in. In these scenarios, you should have the initialization of your class libraries require all of the appropriate data and pass that in from your consuming class's configuration (i.e. ultimately your winform's app.config file).

Answer 2

Your class library will use the config file of the executable that called it.

Answer 3

In a class library, the app.config file is pretty useless. Application setting values get stored in the Settings.settings file and are compiled into the Settings.designer.cs file.

If you modify the value of one of your application settings in app.config directly, that won't have an effect on the setting value seen while running the application. You have to actually open the Settings editor, at which point it will notice the difference between the app.config file and the Settings.settings file and inquire as to whether you'd like it to update your Settings.settings file using values from app.config.

Answer 4

Your default value is stored in the dll.

But let's say you change the setting in code and save it. Where does it get stored for next time?

In WinXP look in:

C:\Documents and Settings\username\Local Settings\Application Data\

or in Windows Vista/7 look in:

C:\Users\username\AppData\Local\

You will find a folder named after your application and drilling down in to that folder, you will find a file named user.config.

For example:

C:\Documents and Settings\username\Local Settings\Application Data\MyApp\myapp.exe_urlla1ii3sytrhx0adqtjnjuc24oacqpgu4\1.0.0.0\user.config