private void Edit_Click(object sender, RoutedEventArgs e)
        {
            var res = GetArticlesFromListBox().FirstOrDefault();
            if (res != null && !_isGroupsVisible)
            {
                var view = new Create(this, isXml, res);
                view.Title = "Редактировать";
                view.ShowDialog();
            }
            else if (_viewingArticle != null)
            {
                var view = new Create(this, isXml, _viewingArticle);
                view.Title = "Редактировать";
                view.ShowDialog();
            }

            if (CreatedArticle != null)
            {
                var art = Articles.First(c => c.ArticleId == CreatedArticle.ArticleId);
                art.ArticleName = CreatedArticle.ArticleName;
                art.InitialText = CreatedArticle.InitialText;
                art.Link = CreatedArticle.Link;
                art.Images = CreatedArticle.Images;
            }
            CreatedArticle = null;
            if (_isGroupsVisible)
            {
                TreeViewHelper.Instance.FillTreeView(Groups, Articles, ArticleTreeView);
                TreeViewHelper.Instance.SelectAndExpand(ArticleTreeView, _viewingArticle);
            }
            else
            {
                CreateListOfArticles(Articles);
            }
            InvokeCounter();
        }
        private void Create_Click(object sender, RoutedEventArgs e)
        {
            var view = new Create(this, isXml);
            view.ShowDialog();
            if (CreatedArticle != null)
            {
                Articles.Add(CreatedArticle);
            }
            if (_isGroupsVisible)
            {
                TreeViewHelper.Instance.FillTreeView(Groups, Articles, ArticleTreeView);
                TreeViewHelper.Instance.SelectAndExpand(ArticleTreeView, CreatedArticle);
            }
            else
            {
                CreateListOfArticles(Articles);
            }

            CreatedArticle = null;
            InvokeCounter();
        }