Pros and cons of AppSettings vs applicationSettings (.NET app.config / Web.config)

The basic <appSettings> is easier to deal with - just slap in a <add key="...." value="..." /> entry and you're done.

The downside is: there's no type-checking, e.g. you cannot safely assume your number that you wanted to configure there really is a number - someone could put a string into that setting..... you just access it as ConfigurationManager["(key)"] and then it's up to you to know what you're dealing with.

Also, over time, the <appSettings> can get rather convoluted and messy, if lots of parts of your app start putting stuff in there (remember the old windows.ini file? :-)).

If you can, I would prefer and recommend using your own configuration sections - with .NET 2.0, it's really become quite easy, That way, you can:

• a) Define your configuration settings in code and have them type-safe and checked
• b) You can cleanly separate YOUR settings from everyone else's. And you can reuse your config code, too!

There's a series of really good articles on you to demystify the .NET 2.0 configuration system on CodeProject:

1. Unraveling the mysteries of .NET 2.0 configuration

2. Decoding the mysteries of .NET 2.0 configuration

3. Cracking the mysteries of .NET 2.0 configuration

Highly recommended! Jon Rista did a great job explaining the configuration system in .NET 2.0.

Application settings can be controlled from a designer (there is usually a Settings.settings file by default) so its easier to modify and you can access them programmatically through the Settings class where they appear like a strongly typed property. You can also have application and user level settings, as well as default settings for rolling back.

This is available from .NET 2.0 onwards and deprecates the other way of doing it (as far as I can tell).

More detail is given at: msdn.microsoft.com/en-us/library/k4s6c3a0.aspx

To understand the pros and cons of settings in the app.config, I suggest that you look into the technical details of both. I have included links where you can find source code for handling, describing more technical details below.

Let me briefly summarize what I recognized when I worked with them (note: the same is applicable to the web.config file of a web site / web application):

applicationSettings in .NET
(click above to view source code and technical details)

Pros

• They allow to store typed data, including object types (via serializeAs property)

• They have a user and application scope, allowing to store default values

• They are supported in Visual Studio's configuration section

• Long strings and/or data with special characters are very well supported (for example, embedded JSON strings containing double quotes)

Cons

• User settings are stored in a different place in the user profile (with a cryptic path), can be difficult to clean up

• Application scope settings are read-only during runtime of the application (only user scope settings can be changed during runtime)

• Read / Write methods code built by Visual Studio's settings designer, not directly provided by 3rd party tools (see link above for a workaround solution)

AppSettings in .NET
Update: AppSettings in .NET Core
(click above to view source code and technical details)

Pros

• Are "light-weight", i.e. easy to handle

• Read and write access during runtime of the application

• They can be edited easily by Administrators in the
  Internet Information Services (IIS) Manager
  ^{(Features View -> Application Settings, note that the name of the icon is misleading since it can only handle AppSettings and not ApplicationSettings)}

Cons

• Support only string data; string length and special characters are limited

• They don't have a user scope

• They don't support default values

• Are not directly supported in Visual Studio's configuration section