A filter used to match elements by their category. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
  Since:  2011 
Syntax
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Remarks
 This filter is a quick filter. Quick filters operate only on the ElementRecord, a low-memory class which has a limited interface to read element properties. Elements which are rejected by a quick filter will not be expanded in memory. 
 Examples
 Copy  C#
 Copy  C# // Find all Wall instances in the document by using category filter
ElementCategoryFilter filter = new ElementCategoryFilter(BuiltInCategory.OST_Walls);
// Apply the filter to the elements in the active document,
// Use shortcut WhereElementIsNotElementType() to find wall instances only
FilteredElementCollector collector = new FilteredElementCollector(document);
IList<Element> walls = collector.WherePasses(filter).WhereElementIsNotElementType().ToElements();
String prompt = "The walls in the current document are:\n";
foreach (Element e in walls)
{
    prompt += e.Name + "\n";
}
TaskDialog.Show("Revit", prompt); Copy  VB.NET
 Copy  VB.NET ' Find all Wall instances in the document by using category filter
Dim filter As New ElementCategoryFilter(BuiltInCategory.OST_Walls)
' Apply the filter to the elements in the active document,
' Use shortcut WhereElementIsNotElementType() to find wall instances only
Dim collector As New FilteredElementCollector(document)
Dim walls As IList(Of Element) = collector.WherePasses(filter).WhereElementIsNotElementType().ToElements()
Dim prompt As [String] = "The walls in the current document are:" & vbLf
For Each e As Element In walls
    prompt += e.Name + vbLf
Next
TaskDialog.Show("Revit", prompt)Inheritance Hierarchy
  System Object  
Autodesk.Revit.DB ElementFilter
Autodesk.Revit.DB ElementQuickFilter
Autodesk.Revit.DB ElementCategoryFilter
 
 Autodesk.Revit.DB ElementFilter
Autodesk.Revit.DB ElementQuickFilter
Autodesk.Revit.DB ElementCategoryFilter