g.DrawLine(Pens.Blue, pt1, pt2);
IPoint pt11 = new ESRI.ArcGIS.Geometry.PointClass();
pt11.X = pt1.X;
pt11.Y = pt1.Y;
IPoint pt21 = new ESRI.ArcGIS.Geometry.PointClass();
pt21.X = pt2.X;
pt21.Y = pt2.Y;
pts.AddPoint(pt11, missing, missing);
pts.AddPoint(pt21, missing, missing);