private async void RefreshContentItems()
        {
            var groups = new ObservableCollection <WorkflowStateGroup> ();

            var workflowStates = await SitecoreHelper.GetWorkflowStatesInWorkflow(Workflow);

            foreach (var workflowState in workflowStates)
            {
                var workflowStateGroup = new WorkflowStateGroup {
                    DisplayName = workflowState.DisplayName
                };
                var contentItems = await SitecoreHelper.GetContentItemsInWorkflowState(workflowState);

                foreach (var contentItem in contentItems)
                {
                    workflowStateGroup.Add(contentItem);
                }

                groups.Add(workflowStateGroup);
            }

            WorkflowStateGroups = groups;
        }