WP7 ListBox: answers to popular questions

published on: 2/4/2011 | Views: N/A | Tags: ListBox

by WindowsPhoneGeek

Today we received several questions about how to use ListBox in WP7. In this mini tutorial we will give our answers:

NOTE: First let me mention that you can take a look at the official MSDN documentation for reference.

Question 1: How to populate ListBox in WP7 in a simple way?

Answer: ListBox is a kind of ItemsControl which you can populate it with data in various ways. Basically you can either populate the ListBox control directly using ListBoxItems, or bind it to a collection of items and use the ItemsSource property. Note that is you want your collection to update its items automatically (add/remove/insert etc. ) a good choice is the ObservableCollection<T>:

“ObservableCollection<T> represents a dynamic data collection that provides notifications when items get added, removed, or when the whole list is refreshed.”

Question 2: How to define ItemsPanel and what is ItemsPanel?

Answer: The ItemsPanel is the the panel used to layout the items in an ItemsControl, and can be anything that derives from the Panel class, even custom panels that you write.The default ListBox template is VirtualizingStackPanel.

“To affect the layout of the items in an ListBox, you use this property to specify a ItemsPanelTemplate.”

Take a look at the below example for reference.

Question 3: Can you give us an example of how to data bind images to my ListBox?

Answer: Take a look at the below example.

Question 4: Can I use external image Uri for my Image?

Answer: You can use external uris but do not forget to set the UriKind.Absolute if you set the image in code behind:

this.logo.Source = new BitmapImage(new Uri(@"http://www.windowsphonegeek.com/upload/appwall/wallimage.png",UriKind.Absolute));

Question 5: How can I use a WrapPanel for the ListBox items layout ?

Answer: You can use the WrapPanel  from the Silverlight for WindowsPhone7 toolkit. We have explained it WrapPanel in depth in this post:

WP7 WrapPanel in depth

Here is the final example.

Example:

<StackPanel x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
    <Image x:Name="logo" Stretch="None"/>
    <TextBlock Text="DataBound ListBox"/>
    <ListBox x:Name="list">
        <ListBox.ItemsPanel>
            <ItemsPanelTemplate>
                <toolkit:WrapPanel/>
            </ItemsPanelTemplate>
        </ListBox.ItemsPanel>
        <ListBox.ItemTemplate>
            <DataTemplate>
                <StackPanel Margin="5">
                    <Image Source="{Binding ImageUri}" Stretch="None"/>
                    <TextBlock Text="{Binding Text}"/>
                </StackPanel>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</StackPanel>

I added several images to the project.The code behind looks like:

public class SampleData
{
    public string Text
    {
        get;
        set;
    }

    public string ImageUri
    {
        get;
        set;
    }
}

public partial class MainPage : PhoneApplicationPage
{    
    public MainPage()
    {
        InitializeComponent();
        ObservableCollection<SampleData> dataSource = new ObservableCollection<SampleData>();
        
        dataSource.Add(new SampleData() { ImageUri = "Images/appbar.close.rest.png", Text = "CLose" });
        dataSource.Add(new SampleData() { ImageUri = "Images/appbar.delete.rest.png", Text = "Delete" });
        dataSource.Add(new SampleData() { ImageUri = "Images/appbar.download.rest.png", Text = "Download" });
        dataSource.Add(new SampleData() { ImageUri = @"http://www.windowsphonegeek.com/upload/appwall/wallimage.png", Text = "Logo" });
        dataSource.Add(new SampleData() { ImageUri = @"http://www.windowsphonegeek.com/upload/appwall/wallimage.png", Text = "Logo" });

        this.list.ItemsSource = dataSource;

        this.logo.Source = new BitmapImage(new Uri(@"http://www.windowsphonegeek.com/upload/appwall/wallimage.png",UriKind.Absolute));
    }
}

I hope that this mini tutorial was helpful. Here is the full source code.

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