Making a WPF TextBox binding fire on each new character?

How can I make a data binding update as soon as a new character is typed in a TextBox? I'm learning about bindings in WPF and now I've become stuck on a (hopefully) simple matter. I have a simple FileLister class where you can set a Path property, and then it will give you a listing of files when you access the FileNames property. Here is that class: ``` class FileLister:INotifyPropertyChanged { private string _path = ""; public string Path { get { return _path; } set { if (_path.Equals(value)) return; _path = value; OnPropertyChanged("Path"); OnPropertyChanged("FileNames"); } } public List<String> FileNames { get { return getListing(Path); } } private List<string> getListing(string path) { DirectoryInfo dir = new DirectoryInfo(path); List<string> result = new List<string>(); if (!dir.Exists) return result; foreach (FileInfo fi in dir.GetFiles()) { result.Add(fi.Name); } return result; } public event PropertyChangedEventHandler PropertyChanged; protected void OnPropertyChanged(string property) { PropertyChangedEventHandler handler = PropertyChanged; if (handler != null) { handler(this, new PropertyChangedEventArgs(property)); } } } ``` I'm using the the FileLister as a StaticResource in this very simple app: ``` <Window x:Class="WpfTest4.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfTest4" Title="MainWindow" Height="350" Width="525"> <Window.Resources> <local:FileLister x:Key="fileLister" Path="d:\temp" /> </Window.Resources> <Grid> <TextBox Text="{Binding Source={StaticResource fileLister}, Path=Path, Mode=TwoWay}" Height="25" Margin="12,12,12,0" VerticalAlignment="Top" /> <ListBox Margin="12,43,12,12" Name="listBox1" ItemsSource="{Binding Source={StaticResource ResourceKey=fileLister}, Path=FileNames}"/> </Grid> </Window> ``` The binding is working. If I change the value in the textbox and then click outside of it, the listbox contents will update (as long as the path exists). The problem is that I would like to update as soon as a new character is typed, and not wait until the textbox lose focus. How can I do that? Is there a way to do this directly in the xaml, or do I have to handle TextChanged or TextInput events on the box?