WPF - bind list to list <string> - what am I doing wrong?
I am trying to do something very basic here, something I would not expect to give me a lot of problems. I have a public property in my main Window class called ItemList, which is of type List<string>
. I have been adding to this list throughout the life of the program and would like the ListBox control I had on my form to automatically update when I add new items to the ItemList property.
So far I have the following XAML:
<Window x:Class="ElserBackupGUI.Main"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Backup Profile Editor [New Profile]" Height="480" Width="640">
<DockPanel>
<Menu DockPanel.Dock="Top">
<MenuItem Header="File">
<MenuItem Header="Open"/>
</MenuItem>
</Menu>
<StackPanel Orientation="Vertical" DockPanel.Dock="Top" Margin="10 10 10 3">
<TextBlock>Items to backup:</TextBlock>
</StackPanel>
<DockPanel DockPanel.Dock="Bottom" Margin="10 0 10 10">
<StackPanel Orientation="Horizontal">
<Button Name="AddDirectoryButton" Height="22.725" Width="120" Margin="0 0 6 0" Click="AddDirectoryButton_Click">Add Directory...</Button>
<Button Name="AddFileButton" Height="22.725" Width="90" Margin="0 0 6 0" Click="AddFileButton_Click">Add File...</Button>
<Button Name="RemoveDirectoriesButton" Height="22.725" Width="75.447" Margin="0 0 6 0">Remove</Button>
</StackPanel>
</DockPanel>
<ListBox Name="SelectedItems" Margin="10 0 10 10" ItemsSource="{Binding Path=ItemList}"/>
</DockPanel>
</Window>
The relevant code-behind looks like this:
public partial class Main : Window
{
private string _lastFolder = string.Empty;
private ObservableCollection<string> _itemList = new ObservableCollection<string>();
public ObservableCollection<string> ItemList {
get { return _itemList ?? (_itemList = new ObservableCollection<string>()); }
set { _itemList = value; }
}
public Main()
{
InitializeComponent();
ItemList.Add("test item");
DataContext = this;
}
private void AddDirectoryButton_Click(object sender, RoutedEventArgs e)
{
FolderBrowserDialog dialog = new FolderBrowserDialog();
if (!string.IsNullOrEmpty(_lastFolder))
dialog.SelectedPath = _lastFolder;
if (dialog.ShowDialog() == System.Windows.Forms.DialogResult.OK)
{
_lastFolder = dialog.SelectedPath;
ItemList.Add(dialog.SelectedPath);
}
}
private void AddFileButton_Click(object sender, RoutedEventArgs e)
{
OpenFileDialog dialog = new OpenFileDialog();
if (!string.IsNullOrEmpty(_lastFolder))
dialog.InitialDirectory = _lastFolder;
if (dialog.ShowDialog() == System.Windows.Forms.DialogResult.OK)
{
_lastFolder = System.IO.Path.GetDirectoryName(dialog.FileName);
SelectedItems.ItemsSource = null;
ItemList.Add(dialog.FileName);
}
}
}
I am relatively new to WPF and most of the tutorials seem too complicated for such a simple problem. I can't seem to find anything here - what am I missing?
source to share
You must use BindingList<T>
or ObservableCollection<T>
instead of List<T>
.
The problem is, in order to bind to a job the way you want it, it needs to implement INotifyCollectionChanged
or IBindingList
. List<T>
doesn't support it.
Edit:
After reviewing the changes, there is still one problem.
In the AddFileButton_Click event handler, remove the following line:
SelectedItems.ItemsSource = null;
It explicitly removes your binding and causes the list box to be removed. If you remove this, your code should work as is.
However, I recommend changing the collection definition and constructor to something more:
// No need for the null checking every time, or public setter. They just cause issues
public ObservableCollection<string> ItemList
{
get;
private set;
}
// Add construction here, now that we're using an auto-prop
public Main()
{
this.ItemList = new ObservableCollection<string>();
InitializeComponent();
ItemList.Add("test item");
DataContext = this;
}
source to share