如果添加了GroupDescriptors, RadGridView在单击一行时会抛出异常

我的RadGridView抛出了一个系统。当有groupdescriptor对网格中的项应用分组时，InvalidCastException。

异常是相当无用的:

[A]DynamicDataType cannot be cast to [B]DynamicDataType. Type A originates from 'DynamicData, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' in the context 'Default' in a byte array. Type B originates from 'DynamicData, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' in the context 'Default' in a byte array.
  at Telerik.Windows.Data.FuncExtensions.<>c__DisplayClass1`2.<ToUntypedFunc>b__0(Object item)
   at Telerik.Windows.Data.QueryableCollectionViewGroup.FindLastLevelGroupByItem(Object item)
   at Telerik.Windows.Controls.GridView.GridViewDataControl.GetRowForItem(Object item, Boolean forceGroupExpand)
   at Telerik.Windows.Controls.GridView.GridViewDataControl.get_CurrentCell()
   at Telerik.Windows.Controls.GridView.GridViewDataControl.CanCellBecomeCurrent(GridViewCell cell)
   at Telerik.Windows.Controls.GridView.GridViewCell.OnMouseLeftButtonDown(MouseButtonEventArgs e)
   at System.Windows.Controls.Control.OnMouseLeftButtonDown(Control ctrl, EventArgs e)
   at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)

当组从网格顶部的条中移除时，就没有问题了，我可以按正常方式选择网格的行。

这个问题似乎与我用来在刷新之间保存griddescriptor的一段代码有关。该方法接受refreshitemsourcelife - timestage，它是一个枚举。此代码在(AboutToRefresh)之前调用，在(FinishedRefresh)之后调用，ItemSource使用适当的参数进行更改。

    public void RefreshGrid(RefreshItemSourceLifetimeStage stage)
    {
        switch (stage)
        {
            case RefreshItemSourceLifetimeStage.AboutToRefresh:
                if (_grid.ItemsSource == null && !_grid.GroupDescriptors.Any())
                {
                    // default group descriptor that you get on initial page load
                    _savedGroupDescriptors.Add(new GroupDescriptor { Member = "_CallFactorSet.CreatedAt.Year", DisplayContent = "Year Created", SortDirection = ListSortDirection.Descending});
                }
                else
                {
                    _savedGroupDescriptors.Clear();
                    foreach (var igd in _grid.GroupDescriptors)
                    {
                        // we have to clone the objects into the _savedGroupDescriptors collection because otherwise they disappear when the itemsource is refreshed
                        if (igd is GroupDescriptor)
                        {
                            var gd = (GroupDescriptor) igd;
                            _savedGroupDescriptors.Add(new GroupDescriptor { Member = gd.Member, DisplayContent = gd.DisplayContent, SortDirection = gd.SortDirection });
                        }
                        else if (igd is ColumnGroupDescriptor)
                        {
                            var cgd = (ColumnGroupDescriptor) igd;
                            _savedGroupDescriptors.Add(new ColumnGroupDescriptor { Column = cgd.Column, DisplayContent = cgd.DisplayContent, SortDirection = cgd.SortDirection });
                        }
                    }
                }
                break;
            case RefreshItemSourceLifetimeStage.FinishedRefresh:
                _grid.GroupDescriptors.Clear();
                foreach(var groupDescriptor in _savedGroupDescriptors)
                {
                    _grid.GroupDescriptors.Add(groupDescriptor);
                }
                break;
            default:
                throw new ArgumentOutOfRangeException("stage");
        }
    }

任何想法?