Get selected Item for Chart

[Rostislaw]

Hi *,

I use a Chart Control (see below)

Items is a collection of Objects with different properties like X, Y, Z and each item has an Id.

My question is how can I get the value of the ID Property having a selected Item (DataPoint) by SelectedValue = "X"? 

All what I have is an object of type SelectionChangedEventArgs contains AddedPoints [SelectionChanged] but there I see only the values I render in the Chart.

Please help.

Thx

R

<telerik:BarSeries ShowLabels="True"
         ValueBinding="{Binding ElementName=radListBox, Path=SelectedValue}"                        ItemsSource="{Binding ElementName=ChartDataSource1}"/>
     ...

<telerik:ChartDataSource  x:Name="ChartDataSource1"                              ItemsSource="{Binding Items ... 

[Martin Ivanov]

Hello Rostislaw,

In order to get the view model of the DataPoint you can use its DataItem property.

var myViewModel = e.AddedPoints[0].DataItem as MyViewModel;
var id = myViewModel.ID;

You can also consider using the SelectedPoints collection of the chart.

I hope this information is useful.

Regards,
Martin
Telerik

[Rostislaw]

Martin, thx for the answer, but in my case this property is null

new System.Collections.Generic.Mscorlib_CollectionDebugView<Telerik.Charting.DataPoint>(e.AddedPoints).Items[0].DataItem Value : null

Am I missing something?

Thanks

Rostislaw

 

[Martin Ivanov]

Hi Rostislaw,

The DataItem property will have a value only if the series' ItemsSource is populated. Otherwise, it will be null. I attached a sample project which demonstrates how you can get the DataItem property. Also, you can take a look at the Create Data-Bound Chart help article.

Regards,
Martin
Telerik

[Rostislaw]

Martin,
Thank you for the example. In your sample app the data item property is not null (as expected).
I found out what the problem is but I do not know if this is an expected behavior.
Working code (data item is valid):
<telerik:BarSeries ShowLabels="True"
                        CategoryBinding="Id"           
                        ValueBinding="{Binding SelectedChart}"
                        ItemsSource="{Binding Items}">

                    </telerik:BarSeries>
Code with data item null: 
<telerik:ChartDataSource  x:Name="ChartDataSource1" ItemsSource="{Binding Items}" />

…

</telerik:BarSeries>

                <telerik:BarSeries ShowLabels="True"   

CategoryBinding="Id"

 ValueBinding="{Binding SelectedChart}"                        

ItemsSource="{Binding ElementName=ChartDataSource1}">                                   

 </telerik:BarSeries>

It looks like the indirection for the ItemSource in XAML does not provide this information.
Anyway for me the problem is solved, thank you for the excellent support.
Rostislaw

[Martin Ivanov]

Hi Rostislaw,

This behavior is expected with RadChartView and its sampling source. ChartDataSource samples the original items which means that it combines several data items into one and the DataItem property doesn't know which one to use. This is why it is empty. However, we have a feature request for adding support for this scenario. You can find it in our feedback portal where you can track its status and vote for its implementation.

Regards,
Martin
Telerik