Is it possible to switch application configuration file at runtime for .NET application?

Question

By default, .NET application's configuration file is named after "exe file name".config. I'm wondering whether it is possible to have one application's configuration specified dynamically.

For example, the built application is "foo.exe". At runtime, the config file is "foo.exe.config". Is it possible to have it accept command line arguments to use other config file. So, the application can use other configuration like below.

foo.exe /config:bar.config

bar.config is used as config file insteand of foo.exe.config.

Answer 1

Yes you will need use ExeConfigurationFileMap

Answer 2

Code from MSDN

static void DisplayMappedExeConfigurationFileSections()
{
    // Get the application configuration file path.
    string exeFilePath = System.IO.Path.Combine(
        Environment.CurrentDirectory, "ConfigurationManager.exe.config");
    // HERE !!!     
    // Map to the application configuration file.
    ExeConfigurationFileMap configFile = new ExeConfigurationFileMap();
    configFile.ExeConfigFilename = exeFilePath;

    Configuration config =
        ConfigurationManager.OpenMappedExeConfiguration(configFile,
        ConfigurationUserLevel.None);

    // Display the configuration file sections.
    ConfigurationSectionCollection sections = config.Sections;

    Console.WriteLine();
    Console.WriteLine("Sections in machine.config:");

    // Loop to get the sections machine.config.
    foreach (ConfigurationSection section in sections)
    {
        string name = section.SectionInformation.Name;
        Console.WriteLine("Name: {0}", name);
    }

}

Answer 3

Gotten from How to use Configuration.GetSection() and ConfigurationManager.OpenMappedExeConfiguration()

ExeConfigurationFileMap fileMap = new ExeConfigurationFileMap();
fileMap.ExeConfigFilename = @"C:\Inetpub\Test\Config\Dev.config";
Configuration config = ConfigurationManager.OpenMappedExeConfiguration(fileMap, ConfigurationUserLevel.None);
AppSettingsSection section = (AppSettingsSection)config.GetSection("appSettings");
string ConfigVersion = section.Settings["ConfigVersion"].Value;

Answer 4

All of the above work well if you need to replace only AppSettings section.

In case you have to run with different config files (all sections) you might want to consider launching application using a host, that creates app domain for your main application and sets different config file depending on parameters you passed in.

Here's the code that worked for me:

        AppDomainSetup setup = new AppDomainSetup();
        setup.ApplicationBase = "file://" + System.Environment.CurrentDirectory;
        setup.DisallowBindingRedirects = true;
        setup.DisallowCodeDownload = true;

        if (args.Length != 0 && args[0].Equals("-test"))
        {
            setup.ConfigurationFile = "PATH_TO_YOUR_TEST_CONFIG_FILE";
        }
        else {
            setup.ConfigurationFile = "PATH_TO_YOUR_LIVE_CONFIG_FILE";
        }

        AppDomain domain = AppDomain.CreateDomain("FRIENDLY_NAME", null, setup);
        domain.ExecuteAssembly("YourMainApp.exe");