CSMSL.Proteomics.AminoAcid.TryGetResidue C# (CSharp) Method

        public static bool TryGetResidue(char letter, out AminoAcid residue)
        {
            residue = null;
            if (letter > 'z' || letter < 0)
                return false;
            residue = ResiduesByLetter[letter];
            return residue != null;
        }

        public static ModificationSites Set(this ModificationSites sites, char aminoacid)
        {
            AminoAcid aa;

            if (AminoAcid.TryGetResidue(aminoacid, out aa))
            {
                sites |= aa.Site;
            }
            return(sites);
        }