public override IRow GetRow(int key, ExCollection collection)
            {
                foreach (var sheetName in SheetNames)
                {
                    var sheet = (IRelationalSheet)collection.GetSheet(sheetName);
                    if (!sheet.Header.DataFileRanges.Any(r => r.Contains(key)))
                    {
                        continue;
                    }

                    var row = RowProducer.GetRow(sheet, key);
                    if (row != null)
                    {
                        return(row);
                    }
                }
                return(null);
            }
            public override IRow GetRow(int key, ExCollection collection)
            {
                var sheet = (IRelationalSheet)collection.GetSheet(SheetName);

                return(RowProducer.GetRow(sheet, key));
            }