Walkthrough: Retrieve Filtered Elements

You can use a filter to select only elements that meet certain criteria. For more information on creating and using element filters, see Iterating the Elements Collection.

This example retrieves all the doors in the document and displays a dialog listing their ids.

Code Region 2-8: Retrieve filtered elements

// Create a Filter to get all the doors in the document
ElementClassFilter familyInstanceFilter = new ElementClassFilter(typeof(FamilyInstance));
ElementCategoryFilter doorsCategoryfilter = 
        new ElementCategoryFilter(BuiltInCategory.OST_Doors);
LogicalAndFilter doorInstancesFilter = 
        new LogicalAndFilter(familyInstanceFilter, doorsCategoryfilter);
FilteredElementCollector collector = new FilteredElementCollector(document);
ICollection<ElementId> doors = collector.WherePasses(doorInstancesFilter).ToElementIds();

String prompt = "The ids of the doors in the current document are:";
foreach(ElementId id in doors)
{
        prompt += "\n\t" + id.IntegerValue;
}

// Give the user some information
TaskDialog.Show("Revit",prompt);