Mine

using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;
using System.IO;
using System.Diagnostics;
using System.Globalization;
using Microsoft.Xna.Framework;
using System.Reflection;

namespace Fds.Xna.Carbine
{
    public class GameSettings
    {
        static Configuration config;

        static GameSettings()
        {
            Process process = Process.GetCurrentProcess();
            string file = process.MainModule.FileName;
            config = ConfigurationManager.OpenExeConfiguration(Path.Combine(Directory.GetCurrentDirectory(), file));
        }
        public static T GetSetValue<T>(string key, T defaultValue) where T : struct
        {
            if (!KeyExists(key))
            {
                SetValue<T>(key, defaultValue);
            }

            return GetValue<T>(key, defaultValue);
        }
        public static T GetValue<T>(string key) where T : struct
        {
            return GetValue<T>(key, default(T));
        }
        public static T GetValue<T>(string key, T defaultValue) where T : struct
        {
            key = key.ToLower();

            T ret = defaultValue;

            if (KeyExists(key))
            {
                string value = config.AppSettings.Settings[key].Value;
                ret = ConvertValue<T>(value);
            }

            return ret;
        }
        public static void SetValue<T>(string key, T value) where T : struct
        {
            key = key.ToLower();

            string valueString = GetValueString<T>(value);

            if (KeyExists(key))
            {
                config.AppSettings.Settings[key].Value = valueString;
            }
            else
            {
                config.AppSettings.Settings.Add(key, valueString);
            }

            config.Save(ConfigurationSaveMode.Modified);
        }
        private static string GetValueString<T>(T value)
        {
            Type type = value.GetType();
            string typeString = type.ToString();

            return String.Format("{0}:{1}", typeString, GetPropertyString<T>(value));
        }
        private static string GetPropertyString<T>(T value)
        {
            string propsString = string.Empty;

            FieldInfo[] fields = value.GetType().GetFields();
            List<FieldInfo> valueFields = new List<FieldInfo>();

            for (int i = 0; i < fields.Length; i++)
            {
                if (!fields[i].IsStatic)
                {
                    valueFields.Add(fields[i]);
                }
            }

            fields = valueFields.ToArray();

            if (fields.Length > 0)
            {
                for (int i = 0; i < fields.Length; i++)
                {
                    FieldInfo info = fields[i];
                    object obj = info.GetValue(value);
                    propsString = string.Concat(propsString, string.Format("{0}|{1}{2}", info.Name, obj.ToString(),
                        ((i + 1 == fields.Length) ? "" : ";")));
                }

                return string.Format("{0}", propsString);
            }
            else
            {
                return value.ToString();
            }
        }
        public static bool KeyExists(string key) 
        {
            key = key.ToLower();
            string[] keys = config.AppSettings.Settings.AllKeys;
            bool exists = false;

            for (int i = 0; (i < keys.Length) && !exists; i++)
            {
                if (keys[i].ToLower() == key)
                {
                    exists = true;
                }
            }

            return exists;
        }
        private static T ConvertValue<T>(string value) where T : struct
        {
            string[] split = value.Split(':');

            if (split.Length != 2)
            {
                throw new Exception("Settings string value was an invalid format");
            }

            string typeString = split[0];
            string valueString = split[1];

            Type type = typeof(T);
            FieldInfo[] fields = type.GetFields();
            List<FieldInfo> valueFields = new List<FieldInfo>();

            for (int i = 0; i < fields.Length; i++)
            {
                if (!fields[i].IsStatic)
                {
                    valueFields.Add(fields[i]);
                }
            }

            fields = valueFields.ToArray();

            if (fields.Length > 0)
            {
                T ret = default(T);
                string[] props = valueString.Split(';');

                foreach(string prop in props)
                {
                    split = prop.Split('|');

                    if (split.Length != 2)
                    {
                        throw new Exception("Value format was invalid");
                    }

                    string propName = split[0];
                    string propValue = split[1];

                    FieldInfo info = type.GetField(prop);
                    info.SetValue(ret, Convert.ChangeType(propValue, info.ReflectedType));
                }

                return ret;
            }
            else
            {
                return (T)Convert.ChangeType(valueString, typeof(T));
            }
        }
    }
}

/*
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="width" value="System.Int32:1024" />
    <add key="height" value="System.Int32:768" />
    <add key="vsync" value="System.Boolean:False" />
    <add key="fullscreen" value="System.Boolean:False" />
    <add key="multisample" value="System.Boolean:False" />
  </appSettings>
</configuration>
*/