This .NET class wraps the AcEdSSGetModes ObjectARX enumeration. 

This enumeration contains the mode settings for an entity selection process. The settings are used by methods that provide notification of a failed entity subselection.

Public Enum SelectionMode
  All = 6
  Box = 3
  Crossing = 2
  CrossingPolygon = 8
  Entity = 5
  Every = 11
  Extents = 12
  FencePolyline = 7
  Group = 13
  Last = 4
  Multiple = 15
  Pick = 10
  Previous = 14
  Window = 1
  WindowPolygon = 9
End Enum

public enum SelectionMode {
  All = 6,
  Box = 3,
  Crossing = 2,
  CrossingPolygon = 8,
  Entity = 5,
  Every = 11,
  Extents = 12,
  FencePolyline = 7,
  Group = 13,
  Last = 4,
  Multiple = 15,
  Pick = 10,
  Previous = 14,
  Window = 1,
  WindowPolygon = 9
}