Question

Hai am using wpf list box, i cannot able to clear the list when am calling the reload data function, i just want to reload new data at runtime,while page loading it loads the data correctly, when i refresh the new data is fetched in itemsource i can see that in debug mode, but no new data in listbox, old data remains in the list, i cant even clear, when i call list.items.clear(), it throws exception and app crashes, i tried lot ways, is ther any problem in my XAML binding, the following is my code.

<DataTemplate x:Key="listBoxTemplate">
                <StackPanel Margin="3">
                    <DockPanel >
                        <TextBlock FontWeight="Bold" Text="{Binding Name}" DockPanel.Dock="Left" Margin="5,0,10,0"/>
                        <TextBlock Text="  " />
                         <TextBlock Text="{Binding Percnt}" Foreground="Green" FontWeight="Bold" />
                   </DockPanel>                       
                </StackPanel>
            </DataTemplate>

My listbox

 <ListBox Height="898" Name="lstEntity" Width="291" ItemTemplate="{StaticResource listBoxTemplate}" SelectionChanged="lstEntity_SelectionChanged"/>

Binding code

   lstEntity.ItemsSource = sei.getNames();

getNames() function just returns the data as list,nothing special code in that, How to resolve this.

Answer 1

The best way to get this type of behavior is to use a DependencyProperty and bindings.

In your class file create the DP like so:

    #region MyList dependency property
    public static readonly DependencyProperty MyListProperty = DependencyProperty.Register("MyList", typeof(ObservableCollection<String>), typeof(Window1));

    public ObservableCollection<String> MyList
    {
        get { return (ObservableCollection<String>) GetValue(MyListProperty); }
        set { SetValue(MyListProperty, value); }
    }
    #endregion

Then in you XAML bind to that DP like so:

<ListBox ItemSource={Binding Path=MyList, ElementName=MyWindow} Height="898" Name="lstEntity" Width="291" ItemTemplate="{StaticResource listBoxTemplate}" SelectionChanged="lstEntity_SelectionChanged"/>

Where “MyWindow” is the x:Name of the root window in you XAML file (you could of course use datacontext like the MVVM pattern as well 🙂

Then if you want to add/remove items from your code you just access the list directly:

MyList.Clear();
MyList.Add("My New String");

You will, of course, also need to change the Generic type of the collection to be your own class…