Discussion Forums

I'm having a problem with the drawing of my layers. It happends on different shape files and when you pan the map it goes away.

I've attached a screenshot of the problem.

I'm using version 6.0.0.47 of the web edition.

Any idea what might be going wrong?

Thanks!

 Hey Gary,

I'm indeed using a ShapeFileFeatureLayer. I have it on different ShapeFileFeatureLayers.

Can I mail you the ShapeFile? I rather not post it in public.

Thanks.

 The weird thing is when I pan the map around I sometimes get this (3 out of 5 times). I've checked this in the Developer tools in Chrome and open the same image again in a new tab and it looks correct. So it gets drawn correctly sometimes but not always.

 Hi Gary,

I've mailed the shape file yesterday.

Regards,

Elm

 Hello Elm,

 Hey Gary,

I've mailed you yesterday with a link to download my sample application.

Thanks,

Elm

Hey Gary,

do you have any news on this issue?

Thanks!

 Hi Gary,

it has been a while since I heard about this issue. Is it still being investigated?

Thanks!

 Hello Elm,

 Hi Gary,

I've send some mails where the problem is more visible.

Thanks!!

Gary,

is there anything I can do to speed this up? I would like to resolve this as soon as possible.

Thanks,

Elm

Hi Elm,

After days searching, we finally find out the problem, the Projection is not thread safe, and it will go wrong in multithread mode sometimes, and here are two ways to solve your problem, 

1), Override the class ManagedProj4Projection and add a locker, but this will not get the advantage of multithread.

    public class MyProjection : ManagedProj4Projection
    {
        static object lockObject = new object();

        protected override Vertex[] ConvertToInternalProjectionCore(double[] x, double[] y)
        {
            lock (lockObject)
            {
                return base.ConvertToInternalProjectionCore(x, y);
            }
        }

        protected override Vertex[] ConvertToExternalProjectionCore(double[] x, double[] y)
        {
            lock (lockObject)
            {
                return base.ConvertToExternalProjectionCore(x, y);
            }
        }
    }

        public MyProjection GetLambert72ToGoogleProjection()
        {
            MyProjection _proj4Lambert72 = new MyProjection();
            _proj4Lambert72.InternalProjectionParametersString = MyProjection.GetEpsgParametersString(31370);
            _proj4Lambert72.ExternalProjectionParametersString = MyProjection.GetGoogleMapParametersString();
            return _proj4Lambert72;
        }

2), Set different instance of projection for each layers to avoid the multithread issue. e.g.

layer1.FeatureSource.Projection = GetLambert72ToGoogleProjection();
layer2.FeatureSource.Projection = GetLambert72ToGoogleProjection();

Hope it helps,

Edgar