Not seeing all the relevant code (how the TrabsientManager obtained, how the point is picked...), it not easy to accurately tell what goes wrong. However, just seeing the code you showed here, it is evidently enough to say that the code would fail, usually not immediately, but would fail at some points when user repeatedly picking points, or run your commands repeatedly. Why, because the code creates non-DB residing entities (Polyline in your case) and never cleans them up. That is, the drawable polyline for TransientGraphics your code generated should be disposed after you are done with the TransientGraphics.
So, it is not good to declare entity variable in a scope of private method and points it to a newly created entity, and then pass the reference over to a object that has bigger scope (TransientManager). This way your code lose the track of the entity it has created and would not be able to clean it up.
Following is the pseudo code I woruld do:
public Point3dCollection PickPointsWithVisualHint(Editor ed, TransientManager tran)
{
Point3dCollection points=new Point3dCollection();
DBObjectCollection drawables=new DbObjectCollection();
while(true)
{
//Set PromptPointOptions
PromptPointResult res=ed.getPoint(options);
if (res.Status==PromptStatus.OK)
(
points.Add(res.Value);
//Create polyline here
Drawable pl=CreatePolyline(res.Value);
//Add the reference to the drawables collection for later clean-up
drawables.Add(pl);
//Draw TransientGraphic
tran.AddTransient(....);
)
else
break;
}
//Clear TransientGraphics after user finishes picking
tran.Erase.....
//Dispose the polylines used for TransientGraphics
if (drawables.Count>0)
{
foreeach (DBObject obj in drawables)
obj.Dispose();
}
return points;
}
Of course, after all points are picked if you still want to keep the TransientGraphic for later operation, you need to delare the "drawables" outside the method and pass it into this method.
I do not know why the TransientGraphics now showing with your code. I tried the code below (in C#, but basically it is identical to yours), which works with my AutoCAD 2012 perfectly:
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.GraphicsInterface;
[assembly: CommandClass(typeof(PickingPointWithVisualHint.MyCommands))]
namespace PickingPointWithVisualHint
{
public class MyCommands
{
private static DBObjectCollection _markers = null;
[CommandMethod("MyPick")]
public static void RunMyCommand()
{
Document dwg = Application.DocumentManager.MdiActiveDocument;
Editor ed = dwg.Editor;
_markers = new DBObjectCollection();
Point3dCollection points = PickPoints(ed);
if (points.Count > 0)
{
ed.WriteMessage("\nPoints picked.");
}
else
{
ed.WriteMessage("\n*Picking cancelled*");
}
Autodesk.AutoCAD.Internal.Utils.PostCommandPrompt();
}
private static Point3dCollection PickPoints(Editor ed)
{
Point3dCollection points = new Point3dCollection();
try
{
while (true)
{
PromptPointOptions opt = new PromptPointOptions("\nSelect a point:");
PromptPointResult res = ed.GetPoint(opt);
if (res.Status==PromptStatus.OK)
{
points.Add(res.Value);
Autodesk.AutoCAD.DatabaseServices.Polyline c =
new Autodesk.AutoCAD.DatabaseServices.Polyline(2);
c.AddVertexAt(0, new Point2d(res.Value.X - 2.5, res.Value.Y), 1.0, 5.0, 5.0);
c.AddVertexAt(1, new Point2d(res.Value.X + 2.5, res.Value.Y), 1.0, 5.0, 5.0);
c.Closed = true;
c.ColorIndex = 1;
_markers.Add(c);
TransientManager tm = TransientManager.CurrentTransientManager;
tm.AddTransient(c, TransientDrawingMode.Main, 0, new IntegerCollection());
}
else
{
break;
}
}
}
finally
{
ClearTransientGraphics();
ed.Regen();
}
return points;
}
private static void ClearTransientGraphics()
{
TransientManager tm = TransientManager.CurrentTransientManager;
if (_markers == null) return;
foreach (DBObject marker in _markers)
{
tm.EraseTransient(marker, new IntegerCollection());
marker.Dispose();
}
_markers = null;
}
}
}
I am not sure what is your purpose to use TransientGraphic, but it is likely the crash was caused because of the Hatch you created not being database-residing and not being disposed.
Whatever your intention is, TransientGraphics may not be suitable to your need (creating it and leaving it there while other CAD operation could be performed and only be gone when AutoCAD does "REDRAW"). It is particular bad that you haave to create non-database-residing entities and leave it in memory, not dispose them. Actually, in your code, there is simply no way to dispose the Hatch.
If you have to achieve the similar visisual effect and clear it at later time, using DrawableOverrule might be much better solution. In your can simply override the WorldDraw() method to fill the polyline with desired color. You set the Overrule's custom filter to user picked polyline.
You can remove the Overrule by a cusom command, or handling CommandWillStart/CommandEnd against particular commands (Redraw/RedrawAll/...).