How to use .NET configuration files (app.config, settings.settings) to save and restore all application data?

Answer 1

I do not think overriding the entire config file is a good idea. Some of the settings in this file might contain settings to be processed really early, before any of your code had a chance to do anything i.e. the ones related to the startup of .NET CLR.

Answer 2

Since you app.config file is a simple xml file you can load it into an XDocument:

string path = AppDomain.CurrentDomain.SetupInformation.ConfigurationFile;
XDocument doc = XDocument.Load(path);
//Do your modifications to section x
doc.Save(path);
ConfigurationManager.RefreshSection("x");

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I corrected the XDocument.Load() code according to @Pat's comment

Answer 3

It is best practice to NOT write to the app.config but use the settings file for saving user settings that are modified. The app.config and web.config should only be used for read only values.

Answer 4

Thanks to Manu's suggestion to just read the file as XML, I hacked together this solution. (It only works for in the current form for properties saved as strings, such as the Text property of a TextBox. It won't work, for instance, if you persist the Value property of a NumericUpDown control.) It works by using Export with a path to the file to save, which produces a file like the following:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <userSettings>
        <HawkConfigGUI.Properties.Settings>
            <setting name="FpgaFilePath" serializeAs="String">
                <value>testfpga</value>
            </setting>
            <setting name="FirmwareFilePath" serializeAs="String">
                <value>test</value>
            </setting>
        </HawkConfigGUI.Properties.Settings>
    </userSettings>
</configuration>

Then you Import the file and all of the settings are changed in the app (don't forget to .Save() at some point). If something goes wrong, the settings will revert back.

using System;
using System.Configuration;
using System.IO;
using System.Linq;
using System.Xml.Linq;
using System.Xml.XPath;
using AedUtils;

namespace HawkConfigGUI
{
    public static class SettingsIO
    {
        private static NLog.Logger _logger = NLog.LogManager.GetCurrentClassLogger();

        internal static void Import(string settingsFilePath)
        {
            if (!File.Exists(settingsFilePath))
            {
                throw new FileNotFoundException();
            }

            var appSettings = Properties.Settings.Default;
            try
            {
                // Open settings file as XML
                var import = XDocument.Load(settingsFilePath);
                // Get the <setting> elements
                var settings = import.XPathSelectElements("//setting");
                foreach (var setting in settings)
                {
                    string name = setting.Attribute("name").Value;
                    string value = setting.XPathSelectElement("value").FirstNode.ToString();

                    try
                    {
                        appSettings[name] = value; // throws SettingsPropertyNotFoundException
                    }
                    catch (SettingsPropertyNotFoundException spnfe)
                    {
                        _logger.WarnException("An imported setting ({0}) did not match an existing setting.".FormatString(name), spnfe);
                    }
                    catch (SettingsPropertyWrongTypeException typeException)
                    {
                        _logger.WarnException(string.Empty, typeException);
                    }
                }
            }
            catch (Exception exc)
            {
                _logger.ErrorException("Could not import settings.", exc);
                appSettings.Reload(); // from last set saved, not defaults
            }
        }

        internal static void Export(string settingsFilePath)
        {
            var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal);
            config.SaveAs(settingsFilePath);
        }
    }
}

Answer 5

Since I did not receive any other answers and was not happy with my previous solution, I asked the question again, did some more research, and was able to come up with a better answer. See How to load a separate Application Settings file dynamically and merge with current settings? for the code and explanation.