MapItemsRequest - The calling thread must be STA, because many UI components require this.

[Julien]

Hello,

 i try to use the MapItemsRequest with the MapPolyline and i have this issue: The calling thread must be STA, because many UI components require this.

public void MapItemsRequest(object sender, MapItemsRequestEventArgs eventArgs)
        {

            double minZoom = eventArgs.MinZoom;
            Location upperLeft = eventArgs.UpperLeft;
            Location lowerRight = eventArgs.LowerRight;

            if(minZoom == 10){
                //GET INFORMATION FROM URL (DownloadString - JSON and parse information)
                var points = new LocationCollection();
                foreach (var coord in feature["geometry"]["coordinates"])
                {
                  points.Add(new Location((double) coord[1], (double) coord[0]));
                }

                var _polyline = new MapPolyline
                {
                   Points = points,
                   Stroke = new SolidColorBrush(Colors.Brown),
                   Name = "id" + feature["_id"],
                   StrokeThickness = 3
                };

                FeaturesList.Add(_polyline);
                eventArgs.CompleteItemsRequest(_trackList);
            }

[Julien]

I created a new post on stackexchange... 

[Petar Mladenov]

Hi Julien,

This framework error might occur if you are using the RadMap with Visualizationlayer's virtualization inside WinForms control (via ElementHost). Generally, In Winforms you can work with UI controls only from the main UI thread.

In your case, I think the UI controls you use in the method are "_polyline" and "FeaturesList". You can try execute this code in Dispatcher.BeginInvoke() block. Also, if you are using VisualizationLayer (VizLayer), you should work with Map Shape Data objects (which are not UI Controls). The MapPolyline control is typical for InformationLayer and should not be used in VizLayer.


Regards,
Petar Mladenov
Telerik