程序代码：

///<summary>
///在＊.exe.config文件中appSettings配置节增加一对键、值对
///</summary>
///<param name="newKey"></param>
///<param name="newValue"></param>
private static void UpdateAppConfig(string newKey, string newValue)
{
    bool isModified = false;    
    foreach (string key in ConfigurationManager.AppSettings)
    {
       if(key==newKey)
        {    
            isModified = true;
        }
    }
 
    // Open App.Config of executable
    Configuration config = 
        ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
    // You need to remove the old settings object before you can replace it
    if (isModified)
    {
        config.AppSettings.Settings.Remove(newKey);
    }    
    // Add an Application Setting.
    config.AppSettings.Settings.Add(newKey,newValue);   
    // Save the changes in App.config file.
    config.Save(ConfigurationSaveMode.Modified);
    // Force a reload of a changed section.
    ConfigurationManager.RefreshSection("appSettings");
}