Blacker.MangaScraper.ViewModel.SettingsWindowViewModel.this C# (CSharp) Метод

        public string this[string columnName]
        {
            get
            {
                columnName = columnName ?? string.Empty;
                if (columnName == string.Empty || columnName == "MaxParallelDownloads")
                {
                    if (MaxParallelDownloads == 0 || MaxParallelDownloads > 50)
                    {
                        return "Maximum number of parallel downloads must be number from 1 to 50.";
                    }
                }
                if (columnName == string.Empty || columnName == "MaxRecentFolders")
                {
                    if (MaxRecentFolders > 50)
                    {
                        return "Maximum number of recent output folders must be number lower or equal to 50.";
                    }
                }
                if (columnName == string.Empty || columnName == "ReaderPath")
                {
                    if (!string.IsNullOrEmpty(ReaderPath) && !System.IO.File.Exists(ReaderPath))
                    {
                        return "File not found on the specified path.";
                    }
                }

                return string.Empty;
            }
        }