public int CompareTo(object iOther) { if (iOther is RoyalGazette) { Int32 retval = 0; RoyalGazette value2 = (RoyalGazette)iOther; retval = Volume.CompareTo(value2.Volume); if (retval == 0) { retval = Issue.CompareTo(value2.Issue); if (retval == 0) { retval = PageInfo.CompareTo(value2.PageInfo); } } return(retval); } throw new InvalidCastException("Not a RoyalGazette"); }