c# 配置文件的读写

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <appSettings>
        <add key="String1" value="value1" />
        <add key="String2" value="value2+" />
        <add key="String1" value="value3" />        
    </appSettings>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
    </startup>
</configuration>

 /// <summary>
 /// 读数配置参数值
 /// </summary>
 /// <param name="key">参数名称</param>
 /// <returns>参数的值</returns>
 public static string ReadConfig(string key)
{
   List<string> list = new List<string>();
   ExeConfigurationFileMap file = new ExeConfigurationFileMap();
   file.ExeConfigFilename = System.Windows.Forms.Application.ExecutablePath + ".config";
   Configuration config = System.Configuration.ConfigurationManager.OpenMappedExeConfiguration(file, ConfigurationUserLevel.None);
   var myApp = (AppSettingsSection)config.GetSection("appSettings");
   return myApp.Settings[key].Value;

}

/// <summary>
/// 写改配置参数中指定参数的值
/// </summary>
/// <param name="key">参数名称</param>
/// <param name="value">参数修改的值</param>
public static void WriteConfig(string key, string value)
{
   ExeConfigurationFileMap file = new ExeConfigurationFileMap();
   file.ExeConfigFilename = System.Windows.Forms.Application.ExecutablePath + ".config";
   Configuration config = System.Configuration.ConfigurationManager.OpenMappedExeConfiguration(file, ConfigurationUserLevel.None);
   var myApp = (AppSettingsSection)config.GetSection("appSettings");
   myApp.Settings[key].Value = value;
   config.Save();
}