public IActionResult Index(string filterAction) { ExerciseDifficulty difficulty; var isValidDifficulty = Enum.TryParse(filterAction.Capitalize(), out difficulty); if (!isValidDifficulty) difficulty = ExerciseDifficulty.Easy | ExerciseDifficulty.Intermediate | ExerciseDifficulty.Hard; var filteredAchievements = _achievementService.FilterAchievements(difficulty); var model = _achivementsViewService.ListAchievements(filteredAchievements); return this.View(model); }