PickObject选择链接DWG图块

believe

叶老师：你好！有一个Revit二次开发的问题，想向您咨询一下！我想控制用户选择链接DWG中的图块,但是却无法选择DWG图块，问题出在什么地方呢

主要代码如下:Selection sel = uiApp.ActiveUIDocument.Selection;
DWGBlockSelectionFilter blockFilter = new DWGBlockSelectionFilter();
Reference refgeo = sel.PickObject(ObjectType.PointOnElement, blockFilter, "请拾取图块");



过滤器：
public bool AllowElement(Element element)
{
    if (element is ImportInstance)
     {
        ImportInstance instance = element as ImportInstance;
        if (instance.IsLinked)
        {
           Reference refer = new Reference(element);
           GeometryObject geometryObject = instance.GetGeometryObjectFromReference(refer);
           if (geometryObject is GeometryInstance)
           {
                  return true;
           }
        }
     }
      return false;
}