AutoCAD COM Application slows down after a specific amount of iterations

Question

I'm working with the AutoCAD COM library to move around blocks so they don't overlap. The way i'm doing it right now is move a selection set around in a circle trying to find an open space, if none was found it expands the circle.

The problem is that after the 387-388 step of this loop it slows down considerably. I added a stopwatch to see where the slowdown was appearing, but the exact location changes if I remove things. I actually removed everything I thought could be slowing it down and that didn't help either. So, at this point I really have no clue why the slow down is consistently happening.

Here is the code I believe is causing the slowdown, let me know if you need more info:

// Selection set
Int16[] filterCode = new Int16[] { 8 };
object[] filterValue = new object[] { LAYERNAME };
selectionSet.Select(AcSelect.acSelectionSetAll, Type.Missing, Type.Missing, filterCode, filterValue)

// This is how I grab the blocks
listOfEntities = new List<AcadEntity>();
foreach(AcadEntity entity in selectionSet)
{
    if(entity.ObjectName.Equals("AcDbBlockReference"))
    {
        AcadBlockReference block = entity as AcadBlockReference;
        if(block.Name.Equals(BLOCKNAME))
            listOfEntities.Add(entity);
    }
    else if(entity.ObjectName.Equals("AcDbText"))
    {
        listOfEntities.add(entity);
    }
}

Then I use a foreach loop to move through the entities in the list and call my function that finds the empty space.

if(listOfEntities.Count > 0)
{
    _thisDrawing.SendCommand("zoom extent ");

    foreach(AcadEntity entity in listOfEntities)
    {
        FindEmptySpace(entity);
    }
}

This is how I move the block around to find the empty space.

radius = (blockHeight > blockWidth ? blockHeight: blockWidth) / 10;

for(double distance = radius; ; distance += radius)
{
    angle = PIx2 / distance;

    for (double currentAngle = angle; currentAngle < PIx2; currentAngle += angle)
    {
         try
         {
             AcadSelectionSet spaceSelection;
             // This ends up being 387-388 every time the slow down starts.
             _totalSteps++;

             // The new location of the block
             newCenterLocation[0] = ((Math.Cos(currentAngle) * distance) + centerLocatoin[0]);
             newCenterLocation[1] = ((Math.Sin(currentAngle) * distance) + centerLocation[1]);

             // The new bounding box points
             newMaxExt[0] = newCenterLocation[0] + (blockWidth / 2);
             newMaxExt[1] = newCenterLocation[1] + (blockHeight / 2);
             newMinExt[0] = newMaxExt[0] - blockWidth;
             newMinExt[1] = newMinExt[1] - blockHeight;

             // Make sure the "SpaceSet" isn't already created.
             // I'm not sure if there is an easier way to do this.
             try
             {
                 _thisDrawing.SelectionSets.Item("SpaceSet").Delete();
             }
             catch
             {}

             spaceSelection = _thisDrawing.SelectionSets.Add("SpaceSet");

             block.Move(centerLocation, newCenterLocation);

             spaceSelection.Select(AcSelect.acSelectionSetCrossing, newMinExt, newMaxExt, Type.Missing, Type.Missing);

             // This is '== 1' because I'm moving the block as well as the selectionset
             if(spaceSelection.Count == 1)
             {
                 spaceSelection.Clear();
                 // Found empty space
                 return;
             }

             spaceSelection.Clear();
             // Empty space wasn't found at this location, move block back.
             // I need to to this because it seems that the Move function moves
             // the blocks based on the difference between the two locations.
             block.Move(newCenterLoaction, centerLocation);
         }
    }
}

I'm not sure If I'm forgetting to do anything. Any help would be appreciated.

Also, I've tried using the 2002 and 2013 versions of the COM, not sure if there is a difference.

UPDATE : While working on the version problem I posted, I got the app to work on 2002. It never slows down while running on AutoCAD 2002. It's the exact same code, the only differences are the library I use and the version number (AutoCAD.Application.15 vs AutoCAD.Application.19). So, there's that.

Answer 1

One tip, rather than use SendCommand, use this for zooming extents (from AutoCAD .NET developer help):

// Zoom to the extents of the current space
Zoom(new Point3d(), new Point3d(), new Point3d(), 1.01075);