相应源码如下所示:

public void SaveConfig(string key, string value)
{
    try
    {
	string fileName = "Web.Config";
	XmlDocument document = new XmlDocument();
	document.Load(fileName);
	((XmlElement)document.SelectSingleNode(@"//AppSetting/add[@key='" + key + "']")).SetAttribute("Value", value);
	document.Save(fileName);
    }
    catch (Exception ex)
    {
	throw new Exception(ex.Message);
    }
}