请教一个关于属性的问题


    public class CaseVO
    {
        public int ID = 0;
        public string CaseNo = string.Empty;        private string m_ExtendXml = string.Empty;
        [JsonIgnore]
        public string ExtendXml
        {
            get
            {
                if(m_ExtendXml == null)
                    m_ExtendXml = SerializationHelper.SerializeToXml(m_Extend);
                return m_ExtendXml;
            }
            set { 
                m_ExtendXml = value;
                m_Extend = (CaseExtendVO)SerializationHelper.DeserializeFromXml(m_ExtendXml, typeof(CaseExtendVO));
            }
        }
        private CaseExtendVO m_Extend = new CaseExtendVO();        public CaseExtendVO Extend
        {
            get
            {
                if(m_Extend == null)
                    m_Extend = (CaseExtendVO)SerializationHelper.DeserializeFromXml(m_ExtendXml, typeof(CaseExtendVO));
                return m_Extend;
            }
            set
            {
                m_Extend = value;
                m_ExtendXml = SerializationHelper.SerializeToXml(value);
            }
        }
    }