将复杂数据绑定到ItemsControl

Question

So basically I have an list of an object that contains another List of objects. Lets say I have an List of the object Class . And Class contains a list of Students . Every student has a property Name as a simple string.

So basically what I want is the following: The user can select a class using a ComboBox.

<ComboBox ItemsSource="{Binding Path=Classes}" DisplayMemberPath="Name" />

That works.

After selecting an Item from that ComboBox, the user should see a list of every student in that class (remember the property Name in Students )

I have created a simple ItemsControl for that purpose.

<ItemsControl ItemsSource="{Binding Classes}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <StackPanel />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Label Content="Name of the Student">
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

My question is: How do I get access to the students name in my label?

Answer 1

Your view model should have a SelectedClass property, which would be updated by binding it to the ComboBox's SelectedItem property:

<ComboBox ItemsSource="{Binding Classes}"
          SelectedItem="{Binding SelectedClass}" .../>

You would then bind the ItemsControl to the Students collection of the selected Class like this:

<ItemsControl ItemsSource="{Binding SelectedClass.Students}">
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Name}"/>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

Note that the view model must implement the INotifyPropertyChanged interface and fire the PropertyChanged event when SelectedClass changes.

---

In a quick and dirty approach without a SelectedClass view model property, you could also directly access the ComboBox's SelectedItem like this:

<ComboBox x:Name="cbClasses" ItemsSource="{Binding Classes}" ... />

<ItemsControl ItemsSource="{Binding SelectedItem.Students, ElementName=cbClasses}">
...