Change config file at runtime

changeconfig.cs

// Set app.config - http://stackoverflow.com/a/6151688/807064
AppDomain.CurrentDomain.SetData("APP_CONFIG_FILE", @"C:\new.config");
typeof(ConfigurationManager)
    .GetField("s_initState", BindingFlags.NonPublic | BindingFlags.Static)
    .SetValue(null, 0);
typeof(ConfigurationManager)
    .GetField("s_configSystem", BindingFlags.NonPublic | BindingFlags.Static)
    .SetValue(null, null);
typeof(ConfigurationManager).Assembly.GetTypes()
    .Where(x => x.FullName == "System.Configuration.ClientConfigPaths")
    .First().GetField("s_current", BindingFlags.NonPublic | BindingFlags.Static)
    .SetValue(null, null);