private int CompareByChromosomeName(SAMRecordField field1, SAMRecordField field2) { string chr1 = field1.Tags.FirstOrDefault(Tag => Tag.Tag.Equals("SN")).Value; string chr2 = field2.Tags.FirstOrDefault(Tag => Tag.Tag.Equals("SN")).Value; return string.Compare(chr1, chr2, StringComparison.Ordinal); } }