Create valid variable name in PascalCase from any text - remove invalid characters, add underscore prefix if needed

CreateName.cs

public static string CreateName(this string s) {
    s = s.Normalize(NormalizationForm.FormD);
    StringBuilder sb = new StringBuilder();
    bool upper = true; 
    for (int i = 0; i < s.Length; i++) 
    {
        var cat = System.Globalization.CharUnicodeInfo.GetUnicodeCategory(s[i]);
        //Console.WriteLine(cat);
        if (cat == System.Globalization.UnicodeCategory.DecimalDigitNumber && sb.Length == 0)
            sb.Append('_');
        if (cat == System.Globalization.UnicodeCategory.LowercaseLetter ||
            cat == System.Globalization.UnicodeCategory.UppercaseLetter ||
            cat == System.Globalization.UnicodeCategory.DecimalDigitNumber)
            sb.Append(upper ? Char.ToUpper(s[i]) : Char.ToLower(s[i]));
        upper = cat != System.Globalization.UnicodeCategory.LowercaseLetter &&
            cat != System.Globalization.UnicodeCategory.UppercaseLetter &&
            cat != System.Globalization.UnicodeCategory.NonSpacingMark;            
    }
 
    return sb.ToString();
}