private void UpdateData(IEnumerable <JiraIssue> issues)
        {
            if (Items == null || issues.Any() == false)
            {
                return;
            }

            _issuesOnChart = issues;
            var newItems = issues.GroupBy(SelectedBase.Selector)
                           .Select(group => new EngagementItem(
                                       group.Key,
                                       SelectedCriteria.Aggregation(group)
                                       ));

            DispatcherHelper.CheckBeginInvokeOnUI(() =>
            {
                Items.Clear();
                foreach (var item in newItems)
                {
                    Items.Add(item);
                }
            });
        }
        private async void UpdateData()
        {
            if (SelectedBase == null || SelectedCriteria == null)
            {
                return;
            }

            var newItems = await Task.Factory.StartNew(() =>
                                                       Issues.GroupBy(SelectedBase.Selector)
                                                       .Select(group => new EngagementItem(group.Key, SelectedCriteria.Aggregation(group))));

            ChartItems.Clear();
            foreach (var item in newItems)
            {
                ChartItems.Add(item);
            }
        }