Bind TextBox on Enter-key press

Question

The default databinding on TextBox is TwoWay and it commits the text to the property only when TextBox lost its focus   Is there any easy XAML way to make the databinding happen when I press the Enter key on the TextBox   I know it is pretty easy to do in the code behind  but imagine if this TextBox is inside some complex DataTemplate

User · Answer

If you combine both Ben and ausadmin s solutions  you end up with a very MVVM friendly solution    lt TextBox Text   Binding Txt1  Mode TwoWay  UpdateSourceTrigger Explicit   gt       lt TextBox InputBindings gt           lt KeyBinding Gesture  Enter                       Command   Binding UpdateTextBoxBindingOnEnterCommand                       CommandParameter   Binding RelativeSource  RelativeSource FindAncestor AncestorType  x Type TextBox       gt       lt  TextBox InputBindings gt   lt  TextBox gt       which means you are passing the TextBox itself as the parameter to the Command   This leads to your Command looking like this  if you re using a DelegateCommand-style implementation in your VM        public bool CanExecuteUpdateTextBoxBindingOnEnterCommand object parameter                return true             public void ExecuteUpdateTextBoxBindingOnEnterCommand object parameter                TextBox tBox   parameter as TextBox          if  tBox    null                        DependencyProperty prop   TextBox TextProperty              BindingExpression binding   BindingOperations GetBindingExpression tBox  prop               if  binding    null                   binding UpdateSource                      This Command implementation can be used for any TextBox and best of all no code in the code-behind though you may want to put this in it s own class so there are no dependencies on System Windows Controls in your VM  It depends on how strict your code guidelines are

User · Answer

You can make yourself a pure XAML approach by creating an attached behaviour   Something like this   public static class InputBindingsManager        public static readonly DependencyProperty UpdatePropertySourceWhenEnterPressedProperty   DependencyProperty RegisterAttached               UpdatePropertySourceWhenEnterPressed   typeof DependencyProperty   typeof InputBindingsManager   new PropertyMetadata null  OnUpdatePropertySourceWhenEnterPressedPropertyChanged         static InputBindingsManager                     public static void SetUpdatePropertySourceWhenEnterPressed DependencyObject dp  DependencyProperty value                dp SetValue UpdatePropertySourceWhenEnterPressedProperty  value              public static DependencyProperty GetUpdatePropertySourceWhenEnterPressed DependencyObject dp                return  DependencyProperty dp GetValue UpdatePropertySourceWhenEnterPressedProperty              private static void OnUpdatePropertySourceWhenEnterPressedPropertyChanged DependencyObject dp  DependencyPropertyChangedEventArgs e                UIElement element   dp as UIElement           if  element    null                        return                     if  e OldValue    null                        element PreviewKeyDown -  HandlePreviewKeyDown                     if  e NewValue    null                        element PreviewKeyDown    new KeyEventHandler HandlePreviewKeyDown                        static void HandlePreviewKeyDown object sender  KeyEventArgs e                if  e Key    Key Enter                        DoUpdateSource e Source                        static void DoUpdateSource object source                DependencyProperty property               GetUpdatePropertySourceWhenEnterPressed source as DependencyObject            if  property    null                        return                     UIElement elt   source as UIElement           if  elt    null                        return                     BindingExpression binding   BindingOperations GetBindingExpression elt  property            if  binding    null                        binding UpdateSource                        Then in your XAML you set the InputBindingsManager UpdatePropertySourceWhenEnterPressedProperty property to the one you want updating when the Enter key is pressed  Like this   lt TextBox Name  itemNameTextBox           Text   Binding Path ItemName  UpdateSourceTrigger PropertyChanged            b InputBindingsManager UpdatePropertySourceWhenEnterPressed  TextBox Text   gt     You just need to make sure to include an xmlns clr-namespace reference for  b  in the root element of your XAML file pointing to which ever namespace you put the InputBindingsManager in

User · Answer

I don t believe that there s any  pure XAML  way to do what you re describing  You can set up a binding so that it updates whenever the text in a TextBox changes  rather than when the TextBox loses focus  by setting the UpdateSourceTrigger property  like this    lt TextBox Name  itemNameTextBox      Text   Binding Path ItemName  UpdateSourceTrigger PropertyChanged     gt    If you set UpdateSourceTrigger to  Explicit  and then handled the TextBox s PreviewKeyDown event  looking for the Enter key  then you could achieve what you want  but it would require code-behind  Perhaps some sort of attached property  similar to my EnterKeyTraversal property  woudld work for you

User · Answer

I personally think having a Markup Extension is a cleaner approach   public class UpdatePropertySourceWhenEnterPressedExtension   MarkupExtension       public override object ProvideValue IServiceProvider serviceProvider                return new DelegateCommand lt TextBox gt  textbox   gt  textbox GetBindingExpression TextBox TextProperty  UpdateSource                     lt TextBox x Name  TextBox               Text   Binding Text   gt           lt TextBox InputBindings gt               lt KeyBinding Key  Enter                          Command   markupExtensions UpdatePropertySourceWhenEnterPressed                            CommandParameter   Binding ElementName TextBox    gt           lt  TextBox InputBindings gt   lt  TextBox gt

User · Answer

In case you are using MultiBinding with your TextBox you need to use BindingOperations GetMultiBindingExpression method instead of BindingOperations GetBindingExpression      Get the correct binding expression based on type of binding    simple binding or multi binding  BindingExpressionBase binding      BindingOperations GetBindingExpression element  prop   if  binding    null        binding   BindingOperations GetMultiBindingExpression element  prop      if  binding    null         object value   element GetValue prop        if  string IsNullOrEmpty value ToString       true                  binding UpdateTarget                else                  binding UpdateSource

User · Answer

This works for me            lt TextBox                              Text   Binding Path UserInput  UpdateSourceTrigger PropertyChanged   gt               lt TextBox InputBindings gt                   lt KeyBinding Key  Return                               Command   Binding Ok    gt               lt  TextBox InputBindings gt           lt  TextBox gt

User · Answer

A different solution  not using xaml but still quite clean I think    class ReturnKeyTextBox   TextBox       protected override void OnKeyUp KeyEventArgs e                base OnKeyUp e           if  e Key    Key Return              GetBindingExpression TextProperty  UpdateSource

User · Answer

Answered here quite elegantly using attached behaviors  my preferred method for almost anything   WPF how to make textbox lose focus after hitting enter

User · Answer

You could easily create your own control inheriting from TextBox and reuse it throughout your project   Something similar to this should work   public class SubmitTextBox   TextBox       public SubmitTextBox             base                 PreviewKeyDown    new KeyEventHandler SubmitTextBox PreviewKeyDown              void SubmitTextBox PreviewKeyDown object sender  KeyEventArgs e                if  e Key    Key Enter                        BindingExpression be   GetBindingExpression TextBox TextProperty               if  be    null                                be UpdateSource                                      There may be a way to get around this step  but otherwise you should bind like this  using Explicit     lt custom SubmitTextBox     Text   Binding Path BoundProperty  UpdateSourceTrigger Explicit     gt

User · Answer

This is not an answer to the original question  but rather an extension of the accepted answer by  Samuel Jack  I did the following in my own application  and was in awe of the elegance of Samuel s solution  It is very clean  and very reusable  as it can be used on any control  not just the TextBox  I thought this should be shared with the community   If you have a Window with a thousand TextBoxes that all require to update the Binding Source on Enter  you can attach this behaviour to all of them by including the XAML below into your Window Resources rather than attaching it to each TextBox  First you must implement the attached behaviour as per Samuel s post  of course     lt Window Resources gt       lt Style TargetType   x Type TextBox   BasedOn   StaticResource  x Type TextBox    gt           lt Style Setters gt               lt Setter Property  b InputBindingsManager UpdatePropertySourceWhenEnterPressed  Value  TextBox Text   gt           lt  Style Setters gt       lt  Style gt   lt  Window Resources gt    You can always limit the scope  if needed  by putting the Style into the Resources of one of the Window s child elements  i e  a Grid  that contains the target TextBoxes

User · Answer

Here is an approach that to me seems quite straightforward  and easier that adding an AttachedBehaviour  which is also a valid solution   We use the default UpdateSourceTrigger  LostFocus for TextBox   and then add an InputBinding to the Enter Key  bound to a command   The xaml is as follows          lt TextBox Grid Row  0  Text   Binding Txt1   Height  30  Width  150  gt           lt TextBox InputBindings gt               lt KeyBinding Gesture  Enter                           Command   Binding UpdateText1Command                           CommandParameter   Binding RelativeSource  RelativeSource FindAncestor AncestorType  x Type TextBox   Path Text     gt           lt  TextBox InputBindings gt       lt  TextBox gt    Then the Command methods are   Private Function CanExecuteUpdateText1 ByVal param As Object  As Boolean     Return True End Function Private Sub ExecuteUpdateText1 ByVal param As Object       If TypeOf param Is String Then         Txt1   CType param  String      End If End Sub   And the TextBox is bound to the Property   Public Property Txt1 As String     Get         Return  txt1     End Get     Set value As String           txt1   value         OnPropertyChanged  Txt1       End Set End Property   So far this seems to work well and catches the Enter Key event in the TextBox

User · Answer

This is how I solved this problem   I created a special event handler that went into the code behind   private void TextBox KeyEnterUpdate object sender  KeyEventArgs e        if  e Key    Key Enter                TextBox tBox    TextBox sender          DependencyProperty prop   TextBox TextProperty           BindingExpression binding   BindingOperations GetBindingExpression tBox  prop           if  binding    null    binding UpdateSource                Then I just added this as a KeyUp event handler in the XAML    lt TextBox Text   Binding TextValue1   KeyUp  TextBox KeyEnterUpdate    gt   lt TextBox Text   Binding TextValue2   KeyUp  TextBox KeyEnterUpdate    gt    The event handler uses its sender reference to cause it s own binding to get updated   Since the event handler is self-contained then it should work in a complex DataTemplate   This one event handler can now be added to all the textboxes that need this feature

[c#] Bind TextBox on Enter-key press

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