鎖定屬性獲取/設置

Question

下面的代碼是否安全，多線程正在訪問屬性但不寫入特定對象。新對象正在創建和分配。多線程調用CreateXmlDoc和ReadXmlDoc

public class DataHolder 
{ 
    public XmlDocument XmlDoc {get; set;} 
} 

public class AccessClass 
{ 
    DataHolder dataHolderInstance; 

    public AccessClass(DataHolder _dataHolder) 
    { 
     dataHolderInstance = _dataHolder; 
    } 

    private void CreateXmlDoc() 
    { 
     XmlDocument _xmlDoc = new XmlDocument(); 
     dataHolderInstance.XmlDoc = _xmlDoc; 
    } 

    private void ReadXmlDoc() 
    { 
     XmlNodeList elemList = dataHolderInstance.XmlDoc.GetElementsByTagName("title"); 
    } 

} 

Answer 1

XML文檔不是線程安全的。 爲了使此代碼線程安全的：

public class DataHolder 
{ 
    object lockObj = new object(); 
    private XmlDocument _xmlDoc; 
    public XmlDocument XmlDoc 
    { 
     get{return GetXmlDoc();} 
     set{SetXmlDoc(value);} 
    } 

    private XmlDocument GetXmlDoc() 
    { 
     lock(lockObj) return _xmlDoc; 
    } 

    private void SetXmlDoc(XmlDocument xmlDoc) 
    { 
     lock(lockObj) _xmlDoc = xmlDoc; 
    } 
} 

public class AccessClass 
{ 
    DataHolder dataHolderInstance; 

    public AccessClass(DataHolder _dataHolder) 
    { 
     dataHolderInstance = _dataHolder; 
    } 

    private void CreateXmlDoc() 
    { 
     XmlDocument _xmlDoc = new XmlDocument(); 
     dataHolderInstance.XmlDoc = _xmlDoc; 
    } 

    private void ReadXmlDoc() 
    { 
     XmlNodeList elemList = dataHolderInstance.XmlDoc.GetElementsByTagName("title"); 
    } 
} 

Answer 2

從純技術的角度來看，因爲你在上面提供的代碼，也不會表現出任何線程安全問題（即數據損壞等）..你要問自己的問題從功能角度來看，需要什麼「線程安全」行爲。