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copied!<p>So, I think the ViewModel Undo/Redo article is a good one, but it's as much as about the ViewModel pattern as it is about how to write custom Undo/Redo functionality. Also, in response to confusedGeek, I think there could be examples where undoing changes in your model, not just in your individual controls is appropriate (say you had a textbox and a slider both bound to the sample property, you want to undo a change regardless of which control made it, so we're talking about app level undo instead of control level).</p> <p>So given that, here is a simple, if not somewhat kludgey example of doing precisely what you ask using a CommandBinding and a simplistic undo stack:</p> <pre><code>public partial class MainWindow : Window { public static readonly DependencyProperty MyStringProperty = DependencyProperty.Register("MyString", typeof(String), typeof(MainWindow), new UIPropertyMetadata("")); // The undo stack Stack<String> previousStrings = new Stack<String>(); String cur = ""; // The current textbox value Boolean ignore = false; // flag to ignore our own "undo" changes public String MyString { get { return (String)GetValue(MyStringProperty); } set { SetValue(MyStringProperty, value); } } public MainWindow() { InitializeComponent(); this.LayoutRoot.DataContext = this; // Using the TextChanged event to add things to our undo stack // This is a kludge, we should probably observe changes to the model, not the UI this.Txt.TextChanged += new TextChangedEventHandler(Txt_TextChanged); // Magic for listening to Ctrl+Z CommandBinding cb = new CommandBinding(); cb.Command = ApplicationCommands.Undo; cb.CanExecute += delegate(object sender, CanExecuteRoutedEventArgs e) { e.CanExecute = true; }; cb.Executed += delegate(object sender, ExecutedRoutedEventArgs e) { if (previousStrings.Count > 0) { ignore = true; this.Txt.Text = previousStrings.Pop(); ignore = false; } e.Handled = true; }; this.CommandBindings.Add(cb); } void Txt_TextChanged(object sender, TextChangedEventArgs e) { if (!ignore) { previousStrings.Push(cur); } cur = this.Txt.Text; } private void SetStr_Click(object sender, RoutedEventArgs e) { this.MyString = "A Value"; } } </code></pre> <p>And here is the XAML:</p> <pre><code><Window x:Class="TestUndoBinding.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525"> <StackPanel Name="LayoutRoot"> <TextBox Name="Txt" Text="{Binding Path=MyString, Mode=TwoWay}" /> <Button Name="SetStr" Click="SetStr_Click">Set to "A Value"</Button> </StackPanel> </Window> </code></pre> <p>In this example the behavior is slightly different than typical TextBox undo behavior because 1) I'm ignoring selection, and 2) I'm not grouping multiple keystrokes into a single undo step, both of which are things you would want to consider in a real app, but should be relatively straightforward to implement yourself.</p>

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