WPF: How to programmatically remove focus from a TextBox

Question

I want to add a simple (at least I thought it was) behaviour to my WPF TextBox.

When the user presses Escape I want the TextBox he is editing to have the text it had when the user started editing, AND I want to remove the focus from the TextBox.

I don't have any problem setting the text for the value it had in the beginning of the edit.

The problem is to remove the focus of the element. I don't want to move the focus to any other component, I just want the TextBox to lose focus. Will I have to have an invisible element to set the focus so my TextBox can lose focus?

Answer 1

in .NET Framework 4 just Keyboard.ClearFocus();

Answer 2

The code I have been using :

// Move to a parent that can take focus
FrameworkElement parent = (FrameworkElement)textBox.Parent;
while (parent != null && parent is IInputElement && !((IInputElement)parent).Focusable)
{
    parent = (FrameworkElement)parent.Parent;
}

DependencyObject scope = FocusManager.GetFocusScope(textBox);
FocusManager.SetFocusedElement(scope, parent as IInputElement);

Answer 3

Since none of the above answers worked for me and the accepted answer does work only for a keyboard focus, I came to the following approach:

// Kill logical focus
FocusManager.SetFocusedElement(FocusManager.GetFocusScope(textBox), null);
// Kill keyboard focus
Keyboard.ClearFocus();

Kills both, logical as well as the keyboard focus.

Answer 4

A bit late to the party, but it was helpful to me so here it goes.

Since .Net 3.0, FrameworkElement has a MoveFocus function which did the trick for me.

Answer 5

You can set the focus to a focusable ancestor. This code will work even if the textbox is inside a template with no focusable ancestors inside that same template:

DependencyObject ancestor = textbox.Parent;
while (ancestor != null)
{
    var element = ancestor as UIElement;
    if (element != null && element.Focusable)
    {
        element.Focus();
        break;
    }

    ancestor = VisualTreeHelper.GetParent(ancestor);
}

Answer 6

AFAIK, it is not possible to completely remove the focus. Something in your Window will always have the focus.

Answer 7

For me, it's quite tricky, especially when using with LostFocus binding. However, my workaround is to add an empty label and focus on it.

<Label Name="ResetFocusArea" Focusable="True" FocusVisualStyle="{x:Null}" />

...

OnKeyDown(object sender, RoutedEventArgs e)
{
  //if is Esc
  ResetFocusArea.Focus();
}

Answer 8

In Windows Phone Development, I just did Focus() or this.Focus() in the PhoneApplicationPage and it worked like a charm.

Answer 9

My answer does not adress the above question directly, however, I feel that the wording of it has caused it to become "The Question" about programmatically getting rid of focus. A common scenario where this is needed is for the user to be able to clear focus upon left-clicking the background of a root control, like window.

So, to achieve this, you can create an Attached Behavior that will switch focus to a dynamically created control (in my case, an empty label). It is preferrable to use this behavior on the highest-level elements like windows, as it iterates through it's children to find a panel it can add a dummy label to.

public class LoseFocusOnLeftClick : Behavior<FrameworkElement>
{
    private readonly MouseBinding _leftClick;
    private readonly Label _emptyControl = new Label() { Focusable = true, HorizontalAlignment = HorizontalAlignment.Left, VerticalAlignment = VerticalAlignment.Top };

    public LoseFocusOnLeftClick()
    {
        _leftClick = new MouseBinding(new RelayCommand(LoseFocus), new MouseGesture(MouseAction.LeftClick));
    }

    protected override void OnAttached()
    {
        AssociatedObject.InputBindings.Add(_leftClick);
        AssociatedObject.Loaded += AssociatedObject_Loaded;
    }        

    protected override void OnDetaching()
    {
        AssociatedObject.InputBindings.Remove(_leftClick);
        AssociatedObject.Loaded -= AssociatedObject_Loaded;
    }

    private void AssociatedObject_Loaded(object sender, RoutedEventArgs e)
    {
        AssociatedObject.Loaded -= AssociatedObject_Loaded;

        AttachEmptyControl();
    }

    private void AttachEmptyControl()
    {            
        DependencyObject currentElement = AssociatedObject;
        while (!(currentElement is Panel))
        {
            currentElement = VisualTreeHelper.GetChild(currentElement, 0);
        }

        ((Panel)currentElement).Children.Add(_emptyControl);
    }

    private void LoseFocus()
    {            
        _emptyControl.Focus();
    }
}

Answer 10

Using LPL's answer worked for me, but it would also make me unable to select any options in dropdown menues. To combat this, I added a check to see if the focused element was a textbox.

Doing the same check for when pressing enter, my final code looked like this:

    public Menu()
    {
        InitializeComponent();
        this.PreviewMouseDown += PreviewMouseDownEventHandler;
        this.KeyDown += WindowKeyDownHandler;
    }
    void ClearFocus()
    {
        UIElement elementWithFocus = Keyboard.FocusedElement as UIElement;
        if (elementWithFocus is System.Windows.Controls.TextBox tb)
        {
            if (Keyboard.FocusedElement != null)
            {
                Keyboard.FocusedElement.RaiseEvent(new RoutedEventArgs(UIElement.LostFocusEvent));
                Keyboard.ClearFocus();
            }
        }
    }

    private void PreviewMouseDownEventHandler(object sender, MouseButtonEventArgs e)
    {
        ClearFocus();
    }
    private void WindowKeyDownHandler(object sender, System.Windows.Input.KeyEventArgs e)
    {
        if (e.Key == Key.Enter)
        {
            ClearFocus();
        }
    }

With this, I didn't need to add a focuslost to every textbox, and it can easily extend to other elements without breaking compatability with other parts of the program.