public void CropAroundRoom(Room room, View view)
{
    if (view != null)
    {
        IList<IList<Autodesk.Revit.DB.BoundarySegment>> segments = room.GetBoundarySegments(new SpatialElementBoundaryOptions());

        if (null != segments)  //the room may not be bound
        {
            foreach (IList<Autodesk.Revit.DB.BoundarySegment> segmentList in segments)
            {
                CurveLoop loop = new CurveLoop();
                foreach (Autodesk.Revit.DB.BoundarySegment boundarySegment in segmentList)
                {
                    loop.Append(boundarySegment.Curve);
                }

                ViewCropRegionShapeManager vcrShapeMgr = view.GetCropRegionShapeManager();
                vcrShapeMgr.SetCropRegionShape(loop);
                break;  // if more than one set of boundary segments for room, crop around the first one
            }
        }
    }
}

Public Sub CropAroundRoom(room As Room, view As View)
    If view IsNot Nothing Then
        Dim segments As IList(Of IList(Of Autodesk.Revit.DB.BoundarySegment)) = room.GetBoundarySegments(New SpatialElementBoundaryOptions())

        If segments IsNot Nothing Then
            'the room may not be bound
            For Each segmentList As IList(Of Autodesk.Revit.DB.BoundarySegment) In segments
                Dim [loop] As New CurveLoop()
                For Each boundarySegment As Autodesk.Revit.DB.BoundarySegment In segmentList
                    [loop].Append(boundarySegment.Curve)
                Next

                Dim vcrShapeMgr As ViewCropRegionShapeManager = view.GetCropRegionShapeManager()
                vcrShapeMgr.SetCropRegionShape([loop])
                ' if more than one set of boundary segments for room, crop around the first one
                Exit For
            Next
        End If
    End If
End Sub