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If I interprete the lisp code correctly, it is used in this scenario:
There is an entity, user picks it, then the routine will get 2 points:
The first one is the point that on the entity closest to where user picks (the pick box could be quite big so that the pick box's centre may not fall on the entity, thus the snap "NEA");
The second point would be an point snapped in "END" mode. depnding on the type of entity, it could be Line's startpoint or endpoint, or LwPolyline's vertex...
So, here is the code to do that:
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Geometry;
[assembly: CommandClass(typeof(SnapPickPoints.MyCommands))]
namespace SnapPickPoints
{
public class MyCommands
{
[CommandMethod("SnapPick")]
public static void SnapPickTest()
{
Document dwg = Application.DocumentManager.MdiActiveDocument;
Editor ed = dwg.Editor;
Point3d pt1, pt2;
if (PickPoints(ed, out pt1, out pt2))
{
ed.WriteMessage("\nFirst Point: x={0}\ty={1}\tz={2}", pt1.X, pt1.Y, pt1.Z);
ed.WriteMessage("\nSecond Point: x={0}\ty={1}\tz={2}", pt2.X, pt2.Y, pt2.Z);
ed.WriteMessage("\n");
}
else
{
ed.WriteMessage("\nCommand: *Cancel*");
}
}
private static bool PickPoints(Editor ed, out Point3d pt1, out Point3d pt2)
{
pt1 = new Point3d();
pt2 = new Point3d();
//Pick an entity
PromptEntityOptions opt = new PromptEntityOptions("\nPick an entity:");
PromptEntityResult res = ed.GetEntity(opt);
if (res.Status != PromptStatus.OK) return false;
//Pick first point with "nea" snap
pt1 = ed.Snap("NEA", res.PickedPoint);
//Pick second point with "end" snap
//AutoCAD will find a closest point (start/end point of Line)
//or vertex of a polyline
pt2 = ed.Snap("END", pt1);
return true;
}
}
}
Start AutoCAD and draw a line/polyline, then run the command.
Is this what you want?
On a second though.
We do not really have to pick an entity to use Editor.Snap(). You can pick anywhere (as point), and pass it to the Snap() method. However, you'd better wrap Editor.Snap() with try..catch block: AutoCAD will try to find a point from a closest entity, based on the snap mode. If the point is too far away from any entity, eInvalidInput exception occurs.
Here is the code:
[CommandMethod("SnapPick1")]
public static void SnapPickTest_1()
{
Document dwg = Application.DocumentManager.MdiActiveDocument;
Editor ed = dwg.Editor;
Point3d pt1, pt2;
if (PickPoints_1(ed, out pt1, out pt2))
{
ed.WriteMessage("\nFirst Point: x={0}\ty={1}\tz={2}", pt1.X, pt1.Y, pt1.Z);
ed.WriteMessage("\nSecond Point: x={0}\ty={1}\tz={2}", pt2.X, pt2.Y, pt2.Z);
ed.WriteMessage("\n");
}
else
{
ed.WriteMessage("\nCommand: *Cancel*");
}
}
private static bool PickPoints_1(Editor ed, out Point3d pt1, out Point3d pt2)
{
pt1 = new Point3d();
pt2 = new Point3d();
//Pick an point near an entity
PromptPointOptions opt = new PromptPointOptions("\nPick a point near an entity:");
PromptPointResult res = ed.GetPoint(opt);
if (res.Status != PromptStatus.OK) return false;
try
{
//Pick first point with "nea" snap
pt1 = ed.Snap("NEA", res.Value);
}
catch
{
ed.WriteMessage("\nPicked point is too far away from an entity. \"NEA\" snap failed.");
return false;
}
//Pick second point with "end" snap
//AutoCAD will find a closest point (start/end point of Line)
//or vertex of a polyline
pt2 = ed.Snap("END", pt1);
return true;
}
When you run this code (make sure you have some lines/polylines drawn), if you pick a point very close to an entity, you get 2 point3d returned; if the picked point is too far away from an entity, the exception is caught in "catch..." clause.
