topic Re: LayerInfo MinScale, MaxScale not being read correctly in ArcGIS API for Silverlight Questions

LayerInfo MinScale, MaxScale not being read correctly

CameronBlandy — Wed, 11 May 2011 19:14:50 GMT

hello,

I am using the following function to read all layers in a Dynamic map service and grab the MinScale and MaxScale properties. The function is very straightforward but doesn't give the desired result. All values for the MinScale and MaxScale are zero.

This is a read only property which is fine as I only want to get the values, not set them.

Does anybody know why this doesn't work.

        private void DynamicLayer_Initialized(object sender, EventArgs e)
        {
            ArcGISDynamicMapServiceLayer mapLayer = sender as ArcGISDynamicMapServiceLayer;
            foreach (LayerInfo li in mapLayer.Layers)
            {
                MessageBox.Show((li.Name + " :" + li.MinScale + " " + li.MaxScale).ToString());
             }
        }

Regards,
Cameron

Re: LayerInfo MinScale, MaxScale not being read correctly

DominiqueBroux — Wed, 11 May 2011 20:29:53 GMT

MinScale and maxScale are only provided by the map service REST end point since ArcGIS server version 10 SP1 (i.e. 10.01).

You can check the version (and the min scale and max scale infos) with a request like : http://services.arcgisonline.com/ArcGIS/rest/services/Demographics/USA_Average_Household_Size/MapServer?f=pjson

Re: LayerInfo MinScale, MaxScale not being read correctly

CameronBlandy — Wed, 11 May 2011 21:08:19 GMT

Thanks for the quick explanation. In the API documentation it doesn't say that those properties are only for 10.1 map services. It would have saved me a lot time if I had know this. 😞

Re: LayerInfo MinScale, MaxScale not being read correctly

CameronBlandy — Sat, 11 Dec 2021 14:06:58 GMT

So I created a function to get the MinScale and MaxScale using json (as found in a previous post).

        private void DynamicLayer_Initialized(object sender, EventArgs e)
        {
            ArcGISDynamicMapServiceLayer mapLayer = sender as ArcGISDynamicMapServiceLayer;

            foreach (LayerInfo li in mapLayer.Layers)
            {
                if (li.SubLayerIds == null)
                {
                    Uri layerUri = new Uri(mapLayer.Url + "/" + li.ID + "?f=json", UriKind.RelativeOrAbsolute);
                    
                    WebClient webClient = new WebClient();
                    webClient.DownloadStringCompleted += webClient_DownloadStringCompleted;
                }  
            }
        }

        public void webClient_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
        {

            string[] properties = e.Result.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
            string minScale = properties.FirstOrDefault(p => p.Contains("minScale"));
            string maxScale = properties.FirstOrDefault(p => p.Contains("maxScale"));

            if (minScale != null)
                minScale = minScale.Substring(minScale.IndexOf(':') + 1, minScale.Length - (minScale.IndexOf(':') + 1));
            if (maxScale != null)
                maxScale = maxScale.Substring(maxScale.IndexOf(':') + 1, maxScale.Length - (maxScale.IndexOf(':') + 1));

        }

The problem I now have is that while it is doing all of the Async calls the Initialized property of the MapService is true which triggers a Map.Layers.LayersInitialized call. I do not want to trigger this event until all of the Aysnc calls have been completed. Is there a way to achieve this?

Regards,
Cameron

Re: LayerInfo MinScale, MaxScale not being read correctly

DominiqueBroux — Fri, 13 May 2011 07:17:33 GMT

which triggers a Map.Layers.LayersInitialized call. I do not want to trigger this event until all of the Aysnc calls have been completed. Is there a way to achieve this?

You can't change the LayersInitialized event.
You have to manage it by yourself. The function that needs the min/max scales should be executed only when the layers are initialized AND when you got the min/max scales for ALL sublayers.

Sidenote : which ArcGIS Server version are you using? If it's the version 10, you can use the layers REST end point (example) which will give you the min/max scales of all the sublayers with only one request. Could be more performant and easier for managing the events.