RVTDocs.com
Namespace: Autodesk.Revit.DB Class: GeometryElement

GeometryElement.GetBoundingBox

Method
Description:
Retrieves a box that encloses the geometry element.
Remarks:

Note: If the GeometryElement was obtained via Element.get_Geometry from an Element containing 2D geometry but no 3D geometry, the bounding box returned by this function may not be empty because it takes the 2D geometry into account.

Syntax 
public BoundingBoxXYZ GetBoundingBox()