Question

I’m trying to link a 2d list of objects to a contentcontrol. I’m getting an exception that I don’t understand. Could someone clarify it for me? (I tried setting the first.ItemsSource property in C# as well to a NationMetrics object that I declared in code – it gave me the same exception)

Outer Exception:

Add value to collection of type ‘System.Windows.Controls.ItemCollection’ threw an exception.

Inner Exception:

Operation is not valid while ItemsSource is in use. Access and modify elements with ItemsControl.ItemsSource instead.

The NationMetrics class:

public class NationMetrics
{
     List<List<Field>> _Nations = new List<List<Field>>();

     public List<List<Field>> Nations { get { return _Nations; } set { _Nations = value; } }

}

Here’s the snippet from my MainWindow.xaml where the exception is being triggered

<Grid>
    <ItemsControl x:Name="first" ItemTemplate="{DynamicResource DataTemplate_Level1}" ItemsSource="{Binding Path=Nations, Source={StaticResource nationMetric}}" />
</Grid>

Here’s the snippet from my Window.Resources which defines nationMetric

<local:NationMetrics x:Name="nm" x:Key="nationMetric" />

Answer 1

You could try out something like this:

<Window.Resources>
    <DataTemplate x:Key="inner">
                    <TextBlock Content="{Binding}"/>
    </DataTemplate>

<DataTemplate x:Key="outer">
    <ItemsControl ItemsSource="{Binding}" ItemTemplate="{DynamicResource inner}">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <StackPanel Orientation="Horizontal"/>
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
    </ItemsControl>
</DataTemplate>

</Window.Resources>

<ItemsControl x:Name="itemControl" ItemsSource="{Binding Path=Nations, Source={StaticResource nationMetric}}" ItemTemplate="{DynamicResource outer}">

This basically identifies that there is a list within in a list and does the binding appropriately. I haven’t tried it, but I think this is the approach!

Other resources:

WPF: How to create a custom items control panel?

Binding 2 dimensional Collection to some control