static TextRuleViewModel()
{
CompositionContainerProvider compositionContainerProvider = new CompositionContainerProvider();
CompositionContainer container = compositionContainerProvider.GetInstance();
_whenNames = container.GetDistinctExportsTypes(typeof(ITextRuleOperationModel), typeof(WhenViewModel)).GetAttributes <DescriptionAttribute>().Select(attr => attr.Description).ToList();
_thenNames = container.GetDistinctExportsTypes(typeof(ITextRuleOperationModel), typeof(ThenViewModel)).GetAttributes <DescriptionAttribute>().Select(attr => attr.Description).ToList();
}