Question

Given a list of objects containing two properties (IdentityType and Name) in the format:

IdentityType | Name
A | One  
A | Two  
A | Three  
B | Four  
B | Five  
C | Six  

Is there a way to declaratively databind that so the accordion displays like this?

A
- One
- Two
- Three
B
- Four
- Five
C
- Six

So far the best I can get is a panel header for each item, like so:

<toolkit:Accordion ItemsSource="{Binding Path=Identities}" Grid.Row="2" SelectionMode="ZeroOrMore">
        <toolkit:Accordion.ItemTemplate>
            <DataTemplate >
                <TextBlock Text="{Binding IdentityType, Converter={StaticResource EnumDescriptionConverter}}"/>
            </DataTemplate>
            </toolkit:Accordion.ItemTemplate>
            <toolkit:Accordion.ContentTemplate>
            <DataTemplate>
                <StackPanel Margin="5" Orientation="Horizontal">
                    <TextBlock Text="{Binding Name}" Foreground="White" />
                </StackPanel>
            </DataTemplate>
        </toolkit:Accordion.ContentTemplate>
    </toolkit:Accordion>

I’m new to Silverlight so I could be missing something blindingly obvious, but any help would be very much appreciated!

Answer 1

You can do this with a view model inbetween your model (the initail list) and your view (the markup).

• Create a view model class with a Title and a NameCollection
• Use LINQ (or a simple foreach) to translate your existing list of 6 entities to a list of 3 entites with 3, 2 and 1 Names in their name collection respectively.
• Bind your Accordions ItemsSource to the collection of ViewModel objects.
• Bind the text block in the your accordion items header template to your Title property
• Add a repeating item control like ItemsControl to your content template of your accordion item
• Bind your repeating item to the NamesCollection

Assuming your model is as follows…

public class Model
{
    public string Title { get; set; }
    public string Name { get; set; }
}

Your View Model structure should be…

public class ViewModel
{
    public string Title { get; set; }
    public List<string> Names { get; set; }
}

public class DataContextClass
{
    public DataContextClass()
    {
        var modelData = new ModelData();

        var query = from m in modelData.ModelCollection
                    group m by m.Title
                    into vm select new ViewModel { Title = vm.Key, Names = vm.Select(x => x.Name).ToList() };
        ViewModelCollection = query.ToList();
    }

    public List<ViewModel> ViewModelCollection { get; set; }
}

Then your view can create an instance of your DataContextClass, assign it to it’s own DataContext property and then use this markup…

<layout:Accordion ItemsSource="{Binding Path=ViewModelDataInstance.ViewModelCollection}" >
    <layout:Accordion.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Title}" />
        </DataTemplate>
    </layout:Accordion.ItemTemplate>
    <layout:Accordion.ContentTemplate>
        <DataTemplate>
            <ItemsControl ItemsSource="{Binding Path=Names}" />
        </DataTemplate>
    </layout:Accordion.ContentTemplate>
</layout:Accordion>