public ICityResult Search(string searchString)
        {
            if (string.IsNullOrEmpty(searchString))
            {
                return(new CityResult());
            }

            var result = _structuredData.Autocomplete(searchString).ToArray();

            return(new CityResult
            {
                NextCities = result.ToArray(),
                NextLetters = GetNextLetters(searchString, result).ToArray()
            });
        }