過濾器過濾元素：

• 建立過濾收集器

Document document = revit.Application.ActiveUIDocument.Document;
FilteredElementCollector collector = new FilteredElementCollector(document);　　

• 過濾元素

1. 快速過濾

   collector.OfCategory(BuiltInCategory.OST_Walls).ofClass(typeof(FamilyInstance))

   OfCategory過濾類別，包括FamilySymbol及FamilyInstance
2. 通用過濾

   LogicalAndFilter doorInstancesFilter =new LogicalAndFilter(familyInstanceFilter, doorsCategoryfilter);
   
   FilteredElementCollector collector = new FilteredElementCollector(document);
   
   ICollection<ElementId> doors = collector.WherePasses(doorInstancesFilter).ToElementIds();

框選構件並篩選構件

public
 
 class WallFilter : ISelectionFilter
{
   public bool AllowElement(Element element)
   {
      if (element is Wall)
      {
         return true;
      }
      return false;
   }
   public bool AllowReference(Reference refer, XYZ point)
   {
      return false;
   }
}
// code in command
IList<Element> elements = uiDoc.Selection.PickElementsByRectangle(new
 
 WallFilter(), "請選擇牆");
foreach (Element element in elements)
{
   // do something
}