public void Change (ExtensionContent alias)
 {
   if (alias.NotNull ()) {
     Category = alias.Category;
     Contents = alias.Contents;
   }
 }
    public void CopyFrom (ExtensionContent alias)
    {
      if (alias.NotNull ()) {
        Id = alias.Id;

        Category = alias.Category;
        Contents = alias.Contents;
      }
    }
 public ExtensionContent (ExtensionContent alias)
   : this ()
 {
   CopyFrom (alias);
 }