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);
}
}