public double MMin {get; set;}

{
  Coordinate2D minCoord = new Coordinate2D(1, 3);
  Coordinate2D maxCoord = new Coordinate2D(2, 4);

  Coordinate2D c1 = new Coordinate2D(0, 5);
  Coordinate2D c2 = new Coordinate2D(1, 3);


  // use the EnvelopeBuilderEx.  This constructor doesn't need to run on the MCT.

  EnvelopeBuilderEx builderEx = new EnvelopeBuilderEx(minCoord, maxCoord);
  // builderEx.XMin, YMin, Zmin, MMin  = 1, 3, 0, double.Nan
  // builderEx.XMax, YMax, ZMax, MMax = 2, 4, 0, double.Nan

  // set XMin.  if XMin > XMax; both XMin and XMax change
  builderEx.XMin = 6;
  // builderEx.XMin, YMin, ZMin, MMin  = 6, 3, 0, double.Nan
  // builderEx.XMax, YMax, ZMax, MMax = 6, 4, 0, double.Nan

  // set XMax
  builderEx.XMax = 8;
  // builderEx.XMin, YMin, ZMin, MMin  = 6, 3, 0, double.Nan
  // builderEx.XMax, YMax, ZMax, MMax = 8, 4, 0, double.Nan

  // set XMax.  if XMax < XMin, both XMin and XMax change
  builderEx.XMax = 3;
  // builderEx.XMin, YMin, ZMin, MMin  = 3, 3, 0, double.Nan
  // builderEx.XMax, YMax, ZMax, MMax = 3, 4, 0, double.Nan

  // set YMin
  builderEx.YMin = 2;
  // builderEx.XMin, YMin, ZMin, MMin  = 3, 2, 0, double.Nan
  // builderEx.XMax, YMax, ZMax, MMax = 3, 4, 0, double.Nan

  // set ZMin.  if ZMin > ZMax, both ZMin and ZMax change
  builderEx.ZMin = 3;
  // builderEx.XMin, YMin, ZMin, MMin  = 3, 2, 3, double.Nan
  // builderEx.XMax, YMax, ZMax, MMax = 3, 4, 3, double.Nan

  // set ZMax.  if ZMax < ZMin. both ZMin and ZMax change
  builderEx.ZMax = -1;
  // builderEx.XMin, YMin, ZMin, MMin  = 3, 2, -1, double.Nan
  // builderEx.XMax, YMax, ZMax, MMax = 3, 4, -1, double.Nan

  builderEx.SetZCoords(8, -5);
  // builderEx.XMin, YMin, ZMin, MMin  = 3, 2, -5, double.Nan
  // builderEx.XMax, YMax, ZMax, MMax = 3, 4, 8, double.Nan


  builderEx.SetXYCoords(c1, c2);
  // builderEx.XMin, YMin, ZMin, MMin  = 0, 3, -5, double.Nan
  // builderEx.XMax, YMax, ZMax, MMax = 1, 5, 8, double.Nan


  builderEx.HasM = true;
  builderEx.SetMCoords(2, 5);

  var geomEx = builderEx.ToGeometry();
}