System.Xml.Serialization.CodeIdentifier.IsValid C# (CSharp) Method

        private static bool IsValid(char c)
        {
            UnicodeCategory uc = CharUnicodeInfo.GetUnicodeCategory(c);
            // each char must be Lu, Ll, Lt, Lm, Lo, Nd, Mn, Mc, Pc
            // 
            switch (uc)
            {
                case UnicodeCategory.UppercaseLetter:        // Lu
                case UnicodeCategory.LowercaseLetter:        // Ll
                case UnicodeCategory.TitlecaseLetter:        // Lt
                case UnicodeCategory.ModifierLetter:         // Lm
                case UnicodeCategory.OtherLetter:            // Lo
                case UnicodeCategory.DecimalDigitNumber:     // Nd
                case UnicodeCategory.NonSpacingMark:         // Mn
                case UnicodeCategory.SpacingCombiningMark:   // Mc
                case UnicodeCategory.ConnectorPunctuation:   // Pc
                    break;
                case UnicodeCategory.LetterNumber:
                case UnicodeCategory.OtherNumber:
                case UnicodeCategory.EnclosingMark:
                case UnicodeCategory.SpaceSeparator:
                case UnicodeCategory.LineSeparator:
                case UnicodeCategory.ParagraphSeparator:
                case UnicodeCategory.Control:
                case UnicodeCategory.Format:
                case UnicodeCategory.Surrogate:
                case UnicodeCategory.PrivateUse:
                case UnicodeCategory.DashPunctuation:
                case UnicodeCategory.OpenPunctuation:
                case UnicodeCategory.ClosePunctuation:
                case UnicodeCategory.InitialQuotePunctuation:
                case UnicodeCategory.FinalQuotePunctuation:
                case UnicodeCategory.OtherPunctuation:
                case UnicodeCategory.MathSymbol:
                case UnicodeCategory.CurrencySymbol:
                case UnicodeCategory.ModifierSymbol:
                case UnicodeCategory.OtherSymbol:
                case UnicodeCategory.OtherNotAssigned:
                    return false;
                default:
#if DEBUG
                    // use exception in the place of Debug.Assert to avoid throwing asserts from a server process such as aspnet_ewp.exe
                    throw new ArgumentException(SR.Format(SR.XmlInternalErrorDetails, "Unhandled category " + uc), "c");
#else
                return false;
#endif
            }
            return true;
        }