topic Re: Identify problem in ArcGIS API for Silverlight Questions

Identify problem

DanielSchatt — Mon, 25 Apr 2011 18:43:15 GMT

I'm trying to use the identify functionality that is in the Identify sample. I have set

LayerOption = LayerOption.Visible

just as in the sample. I assumed this means that all layers are accessible by the identify tool, but only layers that are checked as visible in the web application at any given time will be identified. That's what I want.

But what's happening is that the identify function is only working on the layers that I set as visible in the original .mxd (and which therefore show initially as visible when I load the web site). Those layers will always be identified in the web application whether they are visible or not, and other layers will never be identified whether they are visible or not.

Is this what's supposed to happen? How can I get it to behave as I want? Thanks so much for any help...

Re: Identify problem

DominiqueBroux — Tue, 26 Apr 2011 12:18:11 GMT

Is this what's supposed to happen?

Yes, It's supposed to happen this way.
'LayerOption.Visible' doesn't take care of the layers currently visible at the client side since the identify task is executed at the server side that doesn't know anything about the client.

After setting LayerOption.Visible (without setting the LayerIds), the identify task will work on layers having a default viisbility set to true and being viisble at the current scale.

How can I get it to behave as I want?

You have to set the LayerIds property to the list of currently visible layers.
Once you have set the LayerIds property, you can set the LayerOption.Visible if you want to take care of the visibility depending on the scale.

Re: Identify problem

DanielSchatt — Tue, 26 Apr 2011 18:33:36 GMT

Thanks much Dominique! There may be a better way for me to have done this since I don't know coding very well, but it seems to be working for the most part. For anyone else who may face this issue, I defined a variable for my map service of type ArcGISDynamicMapServiceLayer and then found a line of code on another forum to add only visible layers of the service to the LayerIDs value, as follows:

            ArcGISDynamicMapServiceLayer shorelineAssessmentMapperMapLayer = (ArcGISDynamicMapServiceLayer)ShorelineAssessmentMapperMap.Layers[3];

            ESRI.ArcGIS.Client.Geometry.MapPoint clickPoint = e.MapPoint;

            ESRI.ArcGIS.Client.Tasks.IdentifyParameters identifyParams = new IdentifyParameters()
            {
                Geometry = clickPoint,
                MapExtent = ShorelineAssessmentMapperMap.Extent,
                Width = (int)ShorelineAssessmentMapperMap.ActualWidth,
                Height = (int)ShorelineAssessmentMapperMap.ActualHeight,
                LayerOption = LayerOption.all,
                SpatialReference = ShorelineAssessmentMapperMap.SpatialReference,
            };

            foreach (int x in shorelineAssessmentMapperMapLayer.VisibleLayers)
                identifyParams.LayerIds.Add(x);

            IdentifyTask identifyTask = new IdentifyTask(shorelineAssessmentMapperMapLayer.Url);
            identifyTask.ExecuteCompleted += IdentifyTask_ExecuteCompleted;
            identifyTask.Failed += IdentifyTask_Failed;
            identifyTask.ExecuteAsync(identifyParams);

Re: Identify problem

DominiqueBroux — Wed, 27 Apr 2011 08:04:31 GMT

Great! looks very good.

Optionally you can set LayerOption to LayerOption.viisble if you'd rather to only identify the layers visible at the current scale (but this doesn't change anything if your layers are always visible whatever the scale).

Re: Identify problem

GaryBushek — Thu, 15 Dec 2011 12:45:37 GMT

this works fine in all situations except when none of the layers are visible on the client side. At that point identifyParams.LayerIds is set to have no layers. If thats the case then I get results for all layers visible in the mxd. If I have at least 1 layer specified in the LayerIds array then I get the correct results. Is there a fix for this?

Re: Identify problem

DominiqueBroux — Thu, 15 Dec 2011 15:02:48 GMT

this works fine in all situations except when none of the layers are visible on the client side. Is there a fix for this?

Right. Not really useful to query the server whether we are not expecting any result.

An initial test such as:
if (shorelineAssessmentMapperMapLayer.VisibleLayers.Length == 0) return;
should do the trick:)

Re: Identify problem

GaryBushek — Fri, 16 Dec 2011 00:28:35 GMT

ha!! Sometimes the most obvious things are the easiest to miss. Thanks. I guess I would have just assumed if the array was blank going in that the querytask would respect that and handle it on that end just as if there were 1, 2 or 3 layers to identify.

thanks again.

Re: Identify problem

DominiqueBroux — Fri, 16 Dec 2011 06:38:19 GMT

Yes, the problem is that 'no visible layers' has to be managed as a particular case else we end up with default visible layers.

Re: Identify problem

JannalynPontello — Thu, 20 Sep 2012 13:40:07 GMT

I also need to identify layers that are not visible initially. When I tried to create a variable for my map layers using the suggestions in this thread, I'm getting the error "Cannot convert type 'ESRI.ArcGIS.Client.LayerInfo' to 'ESRI.ArcGIS.Client.ArcGISDynamicMapServiceLayer'.

This is the line with the problem.

ArcGISDynamicMapServiceLayer EMDataLayer = (ArcGISDynamicMapServiceLayer)EMDataLayer.Layers[20];

Re: Identify problem

DominiqueBroux — Thu, 20 Sep 2012 13:49:12 GMT

I'm getting the error "Cannot convert type 'ESRI.ArcGIS.Client.LayerInfo' to 'ESRI.ArcGIS.Client.ArcGISDynamicMapServiceLayer'.

This is the line with the problem.

ArcGISDynamicMapServiceLayer EMDataLayer = (ArcGISDynamicMapServiceLayer)EMDataLayer.Layers[20];

You need to get the layer from the Map, not from the layer itself.

ArcGISDynamicMapServiceLayer EMDataLayer = (ArcGISDynamicMapServiceLayer)myMap.Layers[20];

Though, the code will be clearer if you give an ID to your layer in XAML, so you can reuse this ID by code:

ArcGISDynamicMapServiceLayer EMDataLayer = (ArcGISDynamicMapServiceLayer)myMap.Layers["MyLayerId"];

Re: Identify problem

JannalynPontello — Thu, 20 Sep 2012 14:34:56 GMT

Yes. I didn't read the example carefully enough. I made that changed and used the ID from xaml, but now I'm getting a NullReferenceException on this part.

          foreach (int x in EMDataLayer.VisibleLayers)
          identifyParams.LayerIds.Add(x);

Here's the full code.

private void QueryPoint_Click(object sender, ESRI.ArcGIS.Client.Map.MouseEventArgs e)
        {
            if (IdentifyBtn.IsChecked.Value)
            {
                ArcGISDynamicMapServiceLayer EMDataLayer = (ArcGISDynamicMapServiceLayer)Map.Layers["Data"];

                IdentifyBorder.Visibility = System.Windows.Visibility.Visible;

                ESRI.ArcGIS.Client.Geometry.MapPoint clickPoint = e.MapPoint;

                ESRI.ArcGIS.Client.Tasks.IdentifyParameters identifyParams = new IdentifyParameters()
                {
                        Geometry = clickPoint,
                        MapExtent = Map.Extent,
                        Width = (int)Map.ActualWidth,
                        Height = (int)Map.ActualHeight,
                        LayerOption = LayerOption.all,
                        SpatialReference = Map.SpatialReference
                };

                foreach (int x in EMDataLayer.VisibleLayers)
                identifyParams.LayerIds.Add(x);

                IdentifyTask identifyTask = new IdentifyTask(EMDataLayer.Url);
                identifyTask.ExecuteCompleted += IdentifyTask_ExecuteCompleted;
                identifyTask.Failed += IdentifyTask_Failed;
                identifyTask.ExecuteAsync(identifyParams);

                GraphicsLayer graphicsLayer = Map.Layers["IDGraphicsLayer"] as GraphicsLayer;
                graphicsLayer.ClearGraphics();
                ESRI.ArcGIS.Client.Graphic graphic = new ESRI.ArcGIS.Client.Graphic()
                {
                        Geometry = clickPoint,
                        Symbol = LayoutRoot.Resources["IDPictureSymbol"] as ESRI.ArcGIS.Client.Symbols.Symbol
                };
                graphicsLayer.Graphics.Add(graphic);
            }

Re: Identify problem

DominiqueBroux — Fri, 10 Dec 2021 21:24:35 GMT

Yes. I didn't read the example carefully enough. I made that changed and used the ID from xaml, but now I'm getting a NullReferenceException on this part.

foreach (int x in EMDataLayer.VisibleLayers)
identifyParams.LayerIds.Add(x);

VisibleLayers can be null if you never changed the sublayer visibilities. In this case the default sublayer visibilities are used.

So code like :

if (EMDataLayer.VisibleLayers != null)
  foreach (int x in EMDataLayer.VisibleLayers)
    identifyParams.LayerIds.Add(x);

should work.

Re: Identify problem

JannalynPontello — Thu, 20 Sep 2012 15:20:06 GMT

That fixed the error, but now it seems that the task doesn't use that code. I'm getting all layers whether or not they're visible. I put a break at the foreach statement, but it never gets hit.

Re: Identify problem

DominiqueBroux — Thu, 20 Sep 2012 15:23:04 GMT

LayerOption = LayerOption.all,

You have to use the visible option.

Re: Identify problem

JannalynPontello — Thu, 20 Sep 2012 15:27:53 GMT

I'm using all.

Here's what I've got now.

private void QueryPoint_Click(object sender, ESRI.ArcGIS.Client.Map.MouseEventArgs e)
{
if (IdentifyBtn.IsChecked.Value)
{
ArcGISDynamicMapServiceLayer EMDataLayer = (ArcGISDynamicMapServiceLayer)Map.Layers["Data"];

IdentifyBorder.Visibility = System.Windows.Visibility.Visible;

ESRI.ArcGIS.Client.Geometry.MapPoint clickPoint = e.MapPoint;

ESRI.ArcGIS.Client.Tasks.IdentifyParameters identifyParams = new IdentifyParameters()
{
Geometry = clickPoint,
MapExtent = Map.Extent,
Width = (int)Map.ActualWidth,
Height = (int)Map.ActualHeight,
LayerOption = LayerOption.all,
SpatialReference = Map.SpatialReference
};

if (EMDataLayer.VisibleLayers != null)
foreach (int x in EMDataLayer.VisibleLayers)
identifyParams.LayerIds.Add(x);

IdentifyTask identifyTask = new IdentifyTask(EMDataLayer.Url);
identifyTask.ExecuteCompleted += IdentifyTask_ExecuteCompleted;
identifyTask.Failed += IdentifyTask_Failed;
identifyTask.ExecuteAsync(identifyParams);

GraphicsLayer graphicsLayer = Map.Layers["IDGraphicsLayer"] as GraphicsLayer;
graphicsLayer.ClearGraphics();
ESRI.ArcGIS.Client.Graphic graphic = new ESRI.ArcGIS.Client.Graphic()
{
Geometry = clickPoint,
Symbol = LayoutRoot.Resources["IDPictureSymbol"] as ESRI.ArcGIS.Client.Symbols.Symbol
};
graphicsLayer.Graphics.Add(graphic);
}

Re: Identify problem

DominiqueBroux — Thu, 20 Sep 2012 15:30:46 GMT

I'm using all.

You have to use the 'visible' option (not all) : LayerOption = LayerOption.visible,

With 'all', all layers are identifiable.

Re: Identify problem

JannalynPontello — Thu, 20 Sep 2012 15:37:27 GMT

Got it. I misunderstood. I changed to visible and now it works as I need it. Thanks for your help.

Re: Identify problem

JannalynPontello — Fri, 21 Sep 2012 16:10:16 GMT

Now that I can actually identify all visible layers, I realized there are two layers that I don't want to identify. So I found some code on another thread that checks visibility and can also exclude layers, and now I'm getting duplicate results (actually it shows up six times) in the drop down list for the results window. Do you know why this would happen? I only have the layer in the map one time.

I tried to paste in the new code, but it makes my post too long. How do I attach code so that it shows up in a box?

Re: Identify problem

JannalynPontello — Fri, 21 Sep 2012 17:11:24 GMT

I found the problem. It was in some previous code.

Re: Identify problem

BarraLoubna — Thu, 15 Nov 2012 14:34:45 GMT

I did the same thing as what you have presented here, but there is nothing that displays in my Identify.

Enclosed is my code and the result.

Thank you for your help.