topic Re: How do I get the selected LegendItem? in ArcGIS API for Silverlight Questions

How do I get the selected LegendItem?

KirkKuykendall — Wed, 08 Dec 2010 21:47:10 GMT

When I use the templated legend sample, I see that there is either zero or one selected item in the tree at any given time.

Is there a method on the Legend that returns the currently selected LayerItemViewModel?

Re: How do I get the selected LegendItem?

JenniferNery — Sat, 11 Dec 2021 15:02:11 GMT

We currently do not have SelectionChanged event, you can subscribe to MouseLeftButtonDown event on the container inside DataTemplate and get the LayerItemViewModel this way:

var layerItemViewModel= ((sender as StackPanel).DataContext as ESRI.ArcGIS.Client.Toolkit.Primitives.LayerItemViewModel);

Re: How do I get the selected LegendItem?

DominiqueBroux — Sat, 11 Dec 2021 15:02:14 GMT

The LegendItemViewModel class has a property called 'IsSelected', so, despite that there is no 'SelectionChanged' event (as Jennifer mentionned) if you want to get the selected items, you can loop on all legend items and test this property.

The touchy part is that you have to go though the legend items tree hierarchy.

Example of legend extension class returning the selected items:

public static class LegendExtension
{
    public static IEnumerable<LegendItemViewModel> SelectedItems(this Client.Toolkit.Legend legend)
    {
        if (legend == null)
            return null;
        return legend.LayerItems.Descendants().Where(item => item.IsSelected);
    }
 
    private static IEnumerable<LegendItemViewModel> Descendants(this IEnumerable<LayerItemViewModel> layerItems)
    {
        if (layerItems == null)
            yield break;
 
        foreach (var layerItem in layerItems)
        {
            yield return layerItem;
 
            // return legend items
            if (layerItem.LegendItems != null)
            {
                foreach (var item in layerItem.LegendItems)
                    yield return item;
            }
 
            // return recursively layer items
            if (layerItem.LayerItems != null)
            {
                foreach (var item in layerItem.LayerItems.Descendants())
                    yield return item;
            }
        }
    }
}

Then you can get the Selected items by 'MyLegend.SelectedItems()'.

I see that there is either zero or one selected item in the tree at any given time.

That's true with the default legend template, but we can imagine that one changes it to allow multiple selection. It's why my 'SelectedItems' returns a collection, but you can simplify to only one item if you assume that only one item is selectable at once.

Re: How do I get the selected LegendItem?

AndrewWhite — Thu, 09 Dec 2010 21:50:58 GMT

Here's how I worked around it.

I added a button to the LayerTemplate and on the click event handler, I store the LayerItemViewModel that was clicked.

Re: How do I get the selected LegendItem?

KirkKuykendall — Fri, 10 Dec 2010 17:48:37 GMT

Thanks for the help!

Re: How do I get the selected LegendItem?

JDog — Fri, 25 Mar 2011 03:01:39 GMT

Hi Dominique,
I would like to implement this feature. How or where would I go about plugging this into the Silverlight Toolkit Legend Control? Sorry, I'm new to the Silverlight world as well as the Toolkit.

Any help would be appreciated!

Regards,
JDog

Re: How do I get the selected LegendItem?

DominiqueBroux — Fri, 25 Mar 2011 08:32:18 GMT

To get the selected Legend Item(s), you have first:
1) to put in your project the LegendExtension class code that I gave in this thread
2) call MyLegend.SelectedItems() when you want to get the selected items

You don't have to change the toolkit project, it's only in your project.

Re: How do I get the selected LegendItem?

JDog — Fri, 25 Mar 2011 13:11:09 GMT

Thanks Dominique,
Anybody know a quick fix to port the code to VB.net?

Re: How do I get the selected LegendItem?

dotMorten_esri — Fri, 25 Mar 2011 19:05:56 GMT

http://www.developerfusion.com/tools/convert/csharp-to-vb/

Re: How do I get the selected LegendItem?

JDog — Fri, 25 Mar 2011 20:45:28 GMT

Thanks SharpGIS,
Unfortunately that doesn't convert the "yield" C# which happens to be the difficult part translating to VB.

Re: How do I get the selected LegendItem?

DominiqueBroux — Sat, 11 Dec 2021 15:02:16 GMT

Try with something like:

 
Public NotInheritable Class LegendExtension
Private Sub New()
End Sub
<System.Runtime.CompilerServices.Extension> _
Public Shared Function SelectedItems(legend As Legend) As IEnumerable(Of LegendItemViewModel)
If legend Is Nothing Then
Return Nothing
End If
Return legend.LayerItems.Descendants().Where(Function(item) item.IsSelected)
End Function
 
<System.Runtime.CompilerServices.Extension> _
Private Shared Function Descendants(layerItems As IEnumerable(Of LayerItemViewModel)) As IEnumerable(Of LegendItemViewModel)
Dim result As New List(Of LegendItemViewModel)()
If layerItems Is Nothing Then
Return result
End If
 
For Each layerItem As var In layerItems
result.Add(layerItem)
 
' return legend items
If layerItem.LegendItems IsNot Nothing Then
result.AddRange(layerItem.LegendItems)
End If
 
' return recursively layer items
If layerItem.LayerItems IsNot Nothing Then
result.AddRange(layerItem.LayerItems.Descendants())
End If
Next
Return result
End Function
End Class

Re: How do I get the selected LegendItem?

abdulrenish — Sun, 26 May 2013 06:11:31 GMT

The extension is a good suggestion. For me, i have two map controls, and I use a same Legend (TOC) for selecting layers for the two Maps. When i click on First Map, the legend will popup there and i can select one layer for map 1. And when i right click on mp 2, same legend will popup there, but here I need to disable the Map1 selected layer. Please find me a solution.