When using a Settings.settings file in .NET, where is the config actually stored?

Assuming that you're talking about desktop and not web applications:

When you add settings to a project, VS creates a file named app.config in your project directory and stores the settings in that file. It also builds the Settings.cs file that provides the static accessors to the individual settings.

At compile time, VS will (by default; you can change this) copy the app.config to the build directory, changing its name to match the executable (e.g. if your executable is named foo.exe, the file will be named foo.exe.config), which is the name the .NET configuration manager looks for when it retrieves settings at runtime.

If you change a setting through the VS settings editor, it will update both app.config and Settings.cs. (If you look at the property accessors in the generated code in Settings.cs, you'll see that they're marked with an attribute containing the default value of the setting that's in your app.config file.) If you change a setting by editing the app.config file directly, Settings.cs won't be updated, but the new value will still be used by your program when you run it, because app.config gets copied to foo.exe.config at compile time. If you turn this off (by setting the file's properties), you can change a setting by directly editing the foo.exe.config file in the build directory.

Then there are user-scoped settings.

Application-scope settings are read-only. Your program can modify and save user-scope settings, thus allowing each user to have his/her own settings. These settings aren't stored in the foo.exe.config file (since under Vista, at least, programs can't write to any subdirectory of Program Files without elevation); they're stored in a configuration file in the user's application data directory.

The path to that file is %appdata%\%publisher_name%\%program_name%\%version%\user.config, e.g. C:\Users\My Name\AppData\Local\My_Company\My_Program.exe\1.0.0\user.config. Note that if you've given your program a strong name, the strong name will be appended to the program name in this path.

While browsing around to figure out about the hash in the folder name, I came across (via this answer):

http://blogs.msdn.com/b/rprabhu/archive/2005/06/29/433979.aspx

(edit: Wayback Machine link: https://web.archive.org/web/20160307233557/http://blogs.msdn.com:80/b/rprabhu/archive/2005/06/29/433979.aspx)

The exact path of the user.config files looks something like this:

<Profile Directory>\<Company Name>\<App Name>_<Evidence Type>_<Evidence Hash>\<Version>\user.config

where

<Profile Directory> - is either the roaming profile directory or the local one. Settings are stored by default in the local user.config file. To store a setting in the roaming user.config file, you need to mark the setting with the SettingsManageabilityAttribute with SettingsManageability set to Roaming.

<Company Name> - is typically the string specified by the AssemblyCompanyAttribute (with the caveat that the string is escaped and truncated as necessary, and if not specified on the assembly, we have a fallback procedure).

<App Name> - is typically the string specified by the AssemblyProductAttribute (same caveats as for company name).

<Evidence Type> and <Evidence Hash> - information derived from the app domain evidence to provide proper app domain and assembly isolation.

<Version> - typically the version specified in the AssemblyVersionAttribute. This is required to isolate different versions of the app deployed side by side.

The file name is always simply 'user.config'.

Here is the snippet you can use to programmatically get user.config file location:

public static string GetDefaultExeConfigPath(ConfigurationUserLevel userLevel)
{
  try
  {
    var UserConfig = ConfigurationManager.OpenExeConfiguration(userLevel);
    return UserConfig.FilePath;
  }
  catch (ConfigurationException e)
  {
    return e.Filename;
  }
}

ApplicationSettings (i.e. settings.settings) use PerUserRoamingAndLocal for user settings by default (as I remembered).

Update: Strange but there are too many incorrect answers here. If you are looking for you user scoped settings file (user.config) it will be located in the following folder (for Windows XP):

C:\Documents and Settings\(username)\Local Settings\Application Data\(company-name-if-exists)\(app-name).exe_(Url|StrongName)_(hash)\(app-version)\

Url or StrongName depends on have you application assembly strong name or not.

It depends on whether the setting you have chosen is at "User" scope or "Application" scope.

User scope

User scope settings are stored in

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

You can read/write them at runtime.

For Vista and Windows 7, folder is

C:\Users\ username \AppData\Local\ ApplicationName

or

C:\Users\ username \AppData\Roaming\ ApplicationName

Application scope

Application scope settings are saved in AppName.exe.config and they are readonly at runtime.