Silverlight Combobox - items with a command

Question

What would be the best way to get the elements of a combobox to each support a Command and CommandParameter?

I'd like to implement the Theme Chooser shown toward the bottom of this blog post, except with a combo box instead of a context menu. I'd need each element of the combobox to support a Command and CommandParameter, and I'd like it to just be plain text, as the combo below is.

        <ComboBox>
            <ComboBox.Items>
                <TextBlock>A</TextBlock>
                <TextBlock>B</TextBlock>
                <TextBlock>C</TextBlock>
            </ComboBox.Items>
        </ComboBox>

I tried hyperlinks, but the main problem there is that when you click directly onto the link text, the combo box does not close.

Is there an easy way to do this?

EDIT

Ok, well the specific goal that I said I wanted to achieve—having a combo change the SL Toolkit theme—is trivially accomplished. I can simply bind the selected item of the combo to a ViewModel property that then exposes the appropriate themeuri which my SL Toolkit theme can bind to, or, since this is purely a UI activity with no business logic, I can just catch the combobox item changed event, and update my themeUri from there.

I am curious though, is there a good way to bind each combo box item to a command with a command parameter? Using a Hyperlink as each comboboxItem seemed promising, but that prevents the CB from closing after you click on an item when you click the actual hyperlink.

Do you really need to use a Command or are you just trying to access the change trigger on your ViewModel? — bendewey
I'm trying to change the SL Toolkit Theme dynamically. In thinking about this some more, I think I can just catch the SelectedItemChanged (or whatever) event and do it manually from the code behind. Though this particular question is likely moot, is it actually possible to bind CB items to a command? — Adam Rackis
The reason I ask is because you can just Bind the SelectedItem property to the ComboBox and then your ViewModel can listen to the setter. If you're interested I'll add it as an answer. — bendewey
I'm a little confused because an ICommand binds to a UI action like clicking a button. What UI action are you trying to capture? You would need a UIElement that has an ICommand dependency property or use an attached property. — Jose
@Jose the linked blog post shows a context menu with each of its menu items being bound to a command. I was wondering if there was an easy way to do this with combobox items. From your comment it doesn't sound like this is the case — Adam Rackis

bendewey bendewey · Accepted Answer · 2011-04-26T18:51:52

You could Bind the selected item to your ViewModel and then the setter would trigger when the Theme was changed.

Xaml:

<ComboBox SelectedItem="{Binding SelectedTheme, Mode=TwoWay}" ItemsSource="{Binding Themes}" />

CodeBehind:

public partial class MainPage : UserControl
{
    public MainPage()
    {
        InitializeComponent();

        DataContext = new MainPageViewModel();
    }
}

ViewModel:

public class MainPageViewModel : INotifyPropertyChanged
{
    public ObservableCollection<string> Themes { get; set; }

    private string _selectedTheme;
    public string SelectedTheme
    {
        get { return _selectedTheme; }
        set
        {
            _selectedTheme = value;
            // Change the Theme
            RaisePropertyChanged("SelectedTheme");
        }
    }

    public MainPageViewModel()
    {
        Themes = new ObservableCollection<string>();
        Themes.Add("Red");
        Themes.Add("Green");
        Themes.Add("Blue");
    }
}

Silverlight Combobox - items with a command

1 Answers