/// <summary>
/// 给扩展属性本身的赋值
/// </summary>
/// <param name="propertyName">扩展属性名称</param>
/// <param name="dic">扩展属性的值</param>
public void setExtDic(String propertyName, Dictionary <String, Object> dic)
{
this.set(propertyName, JSON.DicToString(dic));
this.update(propertyName);
}
