How do I select a .Net application configuration file from a command line parameter?

Question

I would like to override the use of the standard app.config by passing a command line parameter. How do I change the default application configuration file so that when I a

Answer 1

This is the relevant part of the source for app that uses default config and accepts override via command line:

Get current or user config into the Config object

Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
string defCfgName = Environment.GetCommandLineArgs()[0] + ".config";

if (arg.Length != 0)
{
    string ConfigFileName = arg[0];
    if (!File.Exists(ConfigFileName))
        Fatal("File doesn't exist: " + ConfigFileName, -1);                
    config = ConfigurationManager.OpenMappedExeConfiguration(new ExeConfigurationFileMap { ExeConfigFilename = ConfigFileName }, ConfigurationUserLevel.None);
}
else if (!File.Exists(defCfgName)) Fatal("Default configuration file doesn't exist and no override is set." , -1);

Use the config object

AppSettingsSection s = (AppSettingsSection)config.GetSection("appSettings");
KeyValueConfigurationCollection a = s.Settings;
ConnectionString = a["ConnectionString"].Value;