public class ClassConfigurationSettings
 {
  public ClassConfigurationSettings()
  {
  }

  /// <summary>
  /// 修改配置文件(数据库连接字符串)
  /// </summary>
  /// <param name="connString"></param>
  public static void UpdateConfig(string p_strKey, string p_strValue)
  {
   try
   {
    string m_strFullPath = "";
    Assembly Asm   = Assembly.GetExecutingAssembly();
    XmlDocument xmlDoc  =new XmlDocument();

    m_strFullPath = Asm.Location.Substring(0, (Asm.Location.LastIndexOf("\\") + 1) ) + "YouApplication.exe.config";
    xmlDoc.Load(m_strFullPath);

    XmlNodeList nodeList=xmlDoc.SelectSingleNode("/configuration/appSettings").ChildNodes;
    foreach(XmlNode xn in nodeList)//遍历所有子节点
    {
     XmlElement xe=(XmlElement)xn;

     if( xe.GetAttribute("key").IndexOf(p_strKey) != -1 )
     {
      xe.SetAttribute("value",p_strValue);
     }
    }
    xmlDoc.Save(m_strFullPath);
   }
   catch(System.NullReferenceException NullEx)
   {
    throw NullEx;
   }
   catch(Exception ex)
   {
    throw ex;
   }
  }

 }