C# App.config vs Settings File

Question

This may sound like a trivial question, however I have looked over the web briefly and what I found was that app.config is basically an older mechanism for storing Application key/pairs of data for the application.

What I want to know is there any reason we (as .NET developers) would opt to use app.config over a Settings file ?

-Can someone please provide some pros and cons on both so we can use them properly.

thanks again

Answer 1

App.config for desktop applications and Web.config for web applications are part of .NET configuration system. Primarily they are used to control .NET framework settings in respect to our application. These are such configuration settings as substitutions of versions of assemblies (section <assemblyBinding>), substitution of .NET framework version (<startup>) etc. (see msdn for the full app.config schema.) One section is dedicated for custom settings of application developers (<appSettings>). There is also a possibility to create custom sections. So, when we need to store settings we can either piggy-back on the app.config or create our own separate configuration files.

Here are pros and contras of using app.config:

1. Pro: There is already a standard API in .NET to read settings from appSettings section. If you only need just a couple of config settings, it is much easier to use this ready API than to develop and test your own class to read your config files. Also, app.config file is already included in VS project for you.

2. Pro: There is a standard hierarchy of machine.config/app.config. If you plan such settings that can be set machine-wide and overridden or left as-is for individual applications, you should use app.config.

3. Pro/Con: App.config is cached in run-time. If you anticipate updates of it while your application is running, you need to specifically request refresh of certain section of config file. For web.config the web app is automatically restarted when something is changed in the file. This is quite convenient.

4. Con: app.config is stored in the same directory as your .exe file. Normally it will be in a subfolder of C:\Program Files. This directory is extra protected in Windows 7 from writing. You need to be member of Administrators group to write there and if your UAC (User Access Control) level in Control Panel is not set to 0 (which normally is not), you will be asked by the OS to confirm writing to c:\Program Files. So, users without Administrator rights will not be able to change configuration in app.config. Same goes for changing your settings programmatically: your application will get exception when attempts to write app.config if it runs not under an admin user on Windows 7. Your own config files usually go to C:\ProgramData\ or c:\Users subfolder (on Windows 7). These locations are friendlier to writing by users or programs.

5. Con: If user edited your app.config file and accidentally corrupted it, the whole application will not start with some obscure error message. If your separate config file is corrupted, you will be able to provide more detailed error message.

In conclusion: app.config gives you easier (faster development) approach, mostly suitable for read-only settings. Custom settings file gives you more freedom (where to store file, validation/error handling, more flexibility with its schema) but requires more work during development.

Answer 2

You have it backwards, the settings file (or ini file as they were originally called) was the mechanism used to hold application settings (key/value pairs) prior to Windows 95. With the release of Windows 95 it was recommended that application settings be moved into the Windows Registry (which proved problematic since if you screwed up your registry your Windows may no longer be able to start).

The .config file came into play with .Net. The XML format allows more dynamic and complex settings configurations than simple key/value pairs.

The modern user/settings file is an XML extension of the .config file (settings that can override certain settings in the .config under specific conditions).