ExportCoachesWithTheirFootballers

        public static string ExportCoachesWithTheirFootballers(FootballersContext context)
        {
            XmlRootAttribute xmlRoot = new XmlRootAttribute("Coaches");
            XmlSerializer xmlSerializer = new XmlSerializer(typeof(ExportCoachDto[]), xmlRoot);

            XmlSerializerNamespaces namespaces = new XmlSerializerNamespaces();
            namespaces.Add(string.Empty, string.Empty);

            StringBuilder sb = new StringBuilder();
            using StringWriter writer = new StringWriter(sb);

            var coaches = context
                .Coaches
                .Where(c => c.Footballers.Any())
                .Select(c => new ExportCoachDto()
                {
                    CoachName = c.Name,
                    FootballersCount = c.Footballers.Count(),
                    Footballers = c.Footballers
                        .Select(f => new ExportCoachFootballerDto()
                        {
                            Name = f.Name,
                            Position = f.PositionType.ToString()
                        })
                        .OrderBy(f => f.Name)
                        .ToArray()
                })
                .OrderByDescending(c => c.FootballersCount)
                .ThenBy(f => f.CoachName)
                .ToArray();
            xmlSerializer.Serialize(writer, coaches, namespaces);
            return sb.ToString().TrimEnd();
        }