Question

I’m unable to do a simple but yet tricky WPF binding in Silverlight 4 (WP7 development)

I have the following code:

Class People{
    public string firstname;
    public string lastname;
}

Class DataSource{
    public static List<People> people; // consider this as a list filled with objects already
}

I’m trying to put the list of people into a ListBox, here’s the xaml I’ve tried:

            <ListBox x:Name="peoplelistbox" Margin="0,0,-12,0" ItemsSource="{Binding DataSource.people}">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                      <StackPanel Margin="0,0,0,17" Width="432">
                            <TextBlock Text="{Binding firstname}" TextWrapping="Wrap"/>
                            <TextBlock Text="{Binding lastname}" TextWrapping="Wrap"/>
                      </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>

But unfortunately my listbox remains empty. What am I doing wrong ?

Thank you in advance 🙂

Cheers,
Miloud B.

Answer 1

Firstly you are using fields, where you should use public property (i.e. people, firstname and lastname). Convert people to a public property, like this:

public static List<People> people { get; set; }

Then, you need to bind the ItemsSource using x:Static markup, like this:

<ListBox x:Name="peoplelistbox" Margin="0,0,-12,0">
   <ListBox.ItemsSource>
      <Binding Source="{x:Static local:DataSource.people}"/>
   <ListBox.ItemsSource/>
   ...

PS: local is the xml namespace pointing to your DataSource class’s namespace. Also, your class too needs to be a public class.

EDIT:
For WP7, you need to declare the instance of the class in the resources and then you can use Path to point to the source. Like this:

<phone:PhoneApplicationPage.Resources>
    <local:DataSource x:Key="dataSource"/>
</phone:PhoneApplicationPage.Resources>
...
<ListBox x:Name="peoplelistbox" Margin="0,0,-12,0" ItemsSource="{Binding Source={StaticResource dataSource}, Path=people}">

PS: Again, your class needs to be public and must have a default constructor.

EDIT:
Here is a example which is working perfectly on my system. Check and see where are you making the mistake:

namespace WindowsPhoneApplication1
{
    public class People
    {
        public string firstname { get; set; }
        public string lastname { get; set; }
    }

    public class DataSource
    {
        public static List<People> people { get; set; }

        public DataSource() { }

        static DataSource()
        {
            people = new List<People> {new People {firstname = "Foo", lastname = "Bar"}};
        }
    }

    public partial class MainPage : PhoneApplicationPage
    {
        // Constructor
        public MainPage()
        {
            InitializeComponent();
        }
    }
}

Xaml (only the relevant portions):

...
...
xmlns:local="clr-namespace:WindowsPhoneApplication1"
...
...
<phone:PhoneApplicationPage.Resources>
    <local:DataSource x:Key="dataSource"/>
</phone:PhoneApplicationPage.Resources>
...
...
<ListBox x:Name="peoplelistbox" Margin="0,0,-12,0" ItemsSource="{Binding Source={StaticResource dataSource}, Path=people}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel Margin="0,0,0,17" Width="432">
                <TextBlock Text="{Binding firstname}" TextWrapping="Wrap"/>
                <TextBlock Text="{Binding lastname}" TextWrapping="Wrap"/>
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>