public override MapPoint ToGeometry()

// Use a builder convenience method or use a builder constructor.

// Builder convenience methods don't need to run on the MCT.
// create a 3d point with M
MapPoint pt = MapPointBuilder.CreateMapPoint(1.0, 2.0, 3.0, 4.0);

MapPoint ptWithM = null;

// Builder constructors need to run on the MCT.
ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
{
  using (MapPointBuilder mb = new MapPointBuilder(1.0, 2.0, 3.0, 4.0))
  {
    // do something with the builder

    ptWithM = mb.ToGeometry();
  }
});

MapPoint clone = ptWithM.Clone() as MapPoint;
MapPoint anotherM = MapPointBuilder.CreateMapPoint(ptWithM);

// Use a builder convenience method or use a builder constructor.

MapPoint point1 = null;

// Builder constructors need to run on the MCT.
ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
{
  using (MapPointBuilder mb = new MapPointBuilder(1.0, 2.0, 3.0))
  {
    bool bhasZ = mb.HasZ;          // hasZ = true
    bool bhasM = mb.HasM;          // hasM = false
    bool bhasID = mb.HasID;        // hasID = false

    // do something with the builder

    point1 = mb.ToGeometry();
  }
});

double x = point1.X;                  // x = 1.0
double y = point1.Y;                  // y = 2.0
double z = point1.Z;                  // z = 3.0
double m = point1.M;                  // m = Nan
int ID = point1.ID;                   // ID = 0
bool hasZ = point1.HasZ;              // hasZ = true
bool hasM = point1.HasM;              // hasM = false
bool hasID = point1.HasID;            // hasID = false
bool isEmpty = point1.IsEmpty;        // isEmpty = false

// Builder convenience methods don't need to run on the MCT.
MapPoint point2 = MapPointBuilder.CreateMapPoint(point1);
x = point2.X;                   // x = 1.0
y = point2.Y;                   // y = 2.0
z = point2.Z;                   // z = 3.0
m = point2.M;                   // m = Nan
hasZ = point2.HasZ;           // hasZ = true
hasM = point2.HasM;           // hasM = false
hasID = point2.HasID;         // hasID = false