AcManager.Controls.UserPresetsControl.SwitchToPrevious C# (CSharp) 메소드

        public void SwitchToPrevious() {
            var presets = SavedPresets;

            var selectedId = presets.FindIndex(x => x.Filename == SelectedPresetFilename);
            if (selectedId == -1) {
                var defaultPreset = _presetable.DefaultPreset;
                CurrentUserPreset = presets.FirstOrDefault(x => x.DisplayName == defaultPreset) ?? presets.FirstOrDefault();
            } else if (--selectedId < 0) {
                CurrentUserPreset = presets.LastOrDefault();
            } else {
                CurrentUserPreset = presets.ElementAtOrDefault(selectedId);
            }
        }