private void RemoveSelectedSprintImp(object obj)
 {
     try {
         SprintDGCollection.Remove(SelectedSprint);
     } catch (Exception ex) {
         MessageBox.Show(ex.Message, "Error", MessageBoxButton.OK, MessageBoxImage.Error);
     }
 }
 private void AddNewSprintImp(object obj)
 {
     try {
         SprintDGCollection.Add(new Sprint(SprintDGCollection.Count() + 1));
     }catch (Exception ex) {
         MessageBox.Show(ex.Message, "Error", MessageBoxButton.OK, MessageBoxImage.Error);
     }
 }