读写app.config AppSettings,保留注释与不保留注释

using System;
using System.Configuration;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
ReadAllSettings();
ReadSetting("Setting1");
ReadSetting("NotValid");
AddUpdateAppSettings("NewSetting", "May 7, 2014");
AddUpdateAppSettings("Setting1", "May 8, 2014");
ReadAllSettings();
}

static void ReadAllSettings()
{
try
{
var appSettings = ConfigurationManager.AppSettings;

if (appSettings.Count == 0)
{
Console.WriteLine("AppSettings is empty.");
}
else
{
foreach (var key in appSettings.AllKeys)
{
Console.WriteLine("Key: {0} Value: {1}", key, appSettings[key]);
}
}
}
catch (ConfigurationErrorsException)
{
Console.WriteLine("Error reading app settings");
}
}

static void ReadSetting(string key)
{
try
{
var appSettings = ConfigurationManager.AppSettings;
string result = appSettings[key] ?? "Not Found";
Console.WriteLine(result);
}
catch (ConfigurationErrorsException)
{
Console.WriteLine("Error reading app settings");
}
}

static void AddUpdateAppSettings(string key, string value)
{
try
{
var configFile = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
var settings = configFile.AppSettings.Settings;
if (settings[key] == null)
{
settings.Add(key, value);
}
else
{
settings[key].Value = value;
}
configFile.Save(ConfigurationSaveMode.Modified);
ConfigurationManager.RefreshSection(configFile.AppSettings.SectionInformation.Name);
}
catch (ConfigurationErrorsException)
{
Console.WriteLine("Error writing app settings");
}
}
}
}

public static void SaveAppSettingsMethod2(string key, string value)
{
//验证key value
//To Do

XmlDocument xml = new XmlDocument();
　　　　　　string configPath = Application.ExecutablePath + ".config";
xml.Load(configPath);

XmlNodeList nodeList = xml.GetElementsByTagName("appSettings");

if (nodeList != null)
{
if (nodeList.Count >= 1)
{
XmlNode node = nodeList[0];
foreach (XmlNode item in node)
{
if (item.NodeType == XmlNodeType.Comment)
{
continue;
}

XmlAttribute xaKey = item.Attributes["key"];
XmlAttribute xaValue = item.Attributes["value"];

if (xaKey != null && xaValue != null && xaKey.Value.Equals(key))
{
xaValue.Value = value;
}
}
}
}
xml.Save(configPath);
}