public class AccessControl()
{
    private static object privateObjectLock = new object();
    public static AccessResult()
    {
       lock(privateObjectLock)
       {
         //數據操作語句
       }
    }
}

class EmailInfo
{
   public static int CurrentNumber;
}

_CurrentNumber=++EmailInfo.CurrentNumber;

lock(this)
{
   _CurrentNumber=++EmailInfo.CurrentNumber;
}

class EmailInfo
{
   public static object syncRoot = new object();
   public static int CurrentNumber;
}

lock(EmailInfo.syncRoot)
{
   _CurrentNumber=++EmailInfo.CurrentNumber;
}