ConfigurationManager.AppSettings Caching

Question

We know that IIS caches ConfigurationManager.AppSettings so it reads the disk only once until the web.config is changed. This is done for performance purposes.

Someo

Answer 1

Try it,

ConfigurationManager.RefreshSection("appSettings")

Just be careful file name (in bin folder)

Normal file name : appname.exe.config

if debug mode : appname.vshost.exe.Config

Answer 2

AppSettings is cached. You can improve performance by further caching to limit namevaluecollection lookups.

See: DotNetPearls Static Config Pattern

Answer 3

It reads the application configuration file (MyApp.exe.config) once at application startup, as can easily be verified by changing the file while the app is running.

The comment in the forum post referenced by the OP was:

The values for the Web.config are stored into cache/memory when the application starts hence why the app restarts when any changes are made to the web.config. Note that this only applies to the Web.config, any other .config files you may use are accessed from the disk by default

I would interpret this comment as meaning that config files other than web.config in an ASP.NET application are accessed from the disk by default. And similarly, config files other than MyApp.exe.config in a WinForms/Console application are accessed from the disk by default.

This comment is not stating that MyApp.exe.config is read from the disk by default.

Answer 4

A quick test seems to show that these settings are only loaded at application startup.

//edit the config file now.
Console.ReadLine();

Console.WriteLine(ConfigurationManager.AppSettings["ApplicationName"].ToString());
Console.WriteLine("Press enter to redisplay");

//edit the config file again now.
Console.ReadLine();
Console.WriteLine(ConfigurationManager.AppSettings["ApplicationName"].ToString());
Console.ReadLine();

You'll see that all outputs remain the same.

Answer 5

As John says only spend more time on this if you are actually seeing a performance hit.

Also I'm pretty sure that these applications hold the configuration in memory, and to see any changes within a config the application would have to be restarted.

For some further reading about remaining mysteries.

Answer 6

It doesn't matter if it does or not. Don't fix a performance problem if there isn't one.