This is record Autodesk.AutoCAD.GraphicsInterface.GradientType.

Public Enum GradientType
  Linear
  Cylinder
  InvCylinder
  Spherical
  Hemispherical
  Curved
  InvSpherical
  InvHemispherical
  InvCurved
End Enum

public enum GradientType {
  Linear,
  Cylinder,
  InvCylinder,
  Spherical,
  Hemispherical,
  Curved,
  InvSpherical,
  InvHemispherical,
  InvCurved
}