Question

I’ve set my ItemsControl with WrapPanel as:

            <ItemsControl Grid.Row="1" Height="200" Width="420" HorizontalAlignment="Center" Name="itemsMarks" VerticalAlignment="Top">
            <ItemsControl.ItemsPanel>
                <ItemsPanelTemplate>
                    <toolkit:WrapPanel HorizontalAlignment="Center" VerticalAlignment="Center"/>
                </ItemsPanelTemplate>
            </ItemsControl.ItemsPanel>
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <StackPanel>
                    <Image Margin="1"  
                                VerticalAlignment="Center"
                                Source="Images/markg.png"
                                Width="70"
                                Height="70" />
                        <TextBlock TextWrapping="Wrap" Foreground="Black" Text="{Binding timestamp}" FontSize="14" HorizontalAlignment="Center" />
                    </StackPanel>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
         </ItemsControl>

my data is

    private class mark_item
    {
        public mark_item()
        {
            this.timestamp= "";
        }
        public string timestamp { get; set; }
    }

    private List<mark_item> marks;

    itemsMarks.ItemsSource = marks;

List marks is properly created, and WrapPanel contains actually the number of items there are in the list, but TextBlock doesn’t get its Text property set.

What am I missing?

Thanks

Answer 1

You need to declare your mark_item class as public, not private.

Data binding in Silverlight can only access public classes and properties. By declaring the class private, you’re preventing Silverlight from being able to access it.

I took your code as it is and I saw the same behaviour you described. The right number of items were appearing in the ItemsControl but the text was missing. I also saw the following message in the Output window in Visual Studio/Visual Web Developer Express. (I’ve omitted the stacktrace as the message itself is long enough):

System.Windows.Data Error: Cannot get ‘timestamp’ value (type ‘System.String’) from ‘PrivateClassProblem.MainPage+mark_item’ (type ‘PrivateClassProblem.MainPage+mark_item’). BindingExpression: Path=’timestamp’ DataItem=’PrivateClassProblem.MainPage+mark_item’ (HashCode=12905972); target element is ‘System.Windows.Controls.TextBlock’ (Name=”); target property is ‘Text’ (type ‘System.String’).. System.MethodAccessException: Attempt by method ‘System.Windows.CLRPropertyListener.get_Value()’ to access method ‘PrivateClassProblem.MainPage+mark_item.get_timestamp()’ failed.

When I declared the class public, the problem went away.