Reloading .NET config file

Question

I need to reload the configuration file after modifying it. How this can be done using appdomains? A code sample would be useful.

Answer 1

Let's say you have the following config file:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="test" value="1" />
  </appSettings>
</configuration>

Let's try the naive approach first. The following application will try to grab the value of the appSetting named test once per second, and print its value:

static void Main(string[] args)
{
    while(true)
    {
        Console.WriteLine(ConfigurationManager.AppSettings["test"]);
        Thread.Sleep(1000);
    }
}

But alas! While this is running, you'll notice it keeps printing 1, and doesn't pick up any changes.

If you update your code to the following, it will fix this issue, and it will pick up changes whenever you change it:

static void Main(string[] args)
{
    while(true)
    {
        ConfigurationManager.RefreshSection("appSettings");
        Console.WriteLine(ConfigurationManager.AppSettings["test"]);
        Thread.Sleep(1000);
    }
}