Cannot draw temp graphics: "Collection was modified; enumeration operation may not execute"

DanS

I've written an add-in that renders arrows (thousands of arrows) in an effort to find a way around this issue, but I can't seem to find any.  When running the below code the application will crash hard with a non-recoverable exception (also below).  It seems a little better in RS6.04, but will still occur.  I'm currently running RS 6.07.01 and RS API 6.07.01   Any help would be much appreciated.

The code looks something like this:

        private static void SendArrowsToRS()

        {

            int xLimit = 1000;

            int yLimit = 10;

            float xStep = 0.005f;

            float yStep = 0.005f;

            float nextX = 0;

            for (int x = 0; x < xLimit; x++)

            {

                float nextY = 0;

                for (int y = 0; y < yLimit; y++)

                {

                    var tail = new Vector3(nextX, nextY, 0f);

                    var tip = new Vector3(nextX, nextY, 0.1f);

                    nextY += yStep;

                    Thread.Sleep(20);

                    Station.ActiveStation.TemporaryGraphics.DrawArrow(tip, tail, 0.01, 3, Color.Black);

                }

                nextX += xStep;

            }

        }

The exception is below.  None of my code shows up in the stacktrace, this seems to be an internal exception as a result of the above code rendering arrows.

System.InvalidOperationException

  HResult=0x80131509

  Message=Collection was modified; enumeration operation may not execute.

  Source=mscorlib

  StackTrace:

   at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)

   at System.Collections.Generic.List`1.Enumerator.MoveNextRare()

   at RobotStudio.Services.Graphics.GfxTempModel.Update(Boolean force)

   at RobotStudio.Services.Graphics.GfxUpdater.UpdateGraphics(IEnumerable`1 gfxModels, Boolean forceRefresh, Boolean& needRedraw)

   at RobotStudio.Services.Graphics.GfxService.UpdateGraphics(IEnumerable`1 models, Boolean force)

   at RobotStudio.Services.Graphics.GfxUpdater.Application_Idle(Object sender, EventArgs e)

   at System.EventHandler.Invoke(Object sender, EventArgs e)

   at System.Windows.Forms.Application.ThreadContext.System.Windows.Forms.UnsafeNativeMethods.IMsoComponent.FDoIdle(Int32 grfidlef)

   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)

   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)

   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)

   at ABBInternal.StudioAppFramework.StudioAppFrameworkHost.Run()

   at RobotStudio.Program.Main(String[] args)

DanS

I've learned that this problem is very intermittent.  The higher the number of temp graphics will increase the likely hood of this occurring.  I can also force the exception if I interact with the graphics view at any time (clicking or pan/zoom).  Please help!

DanS

This ended up being a threading issue...I was on a different thread.