WPF：ComboBox F4键未在KeyDown事件中触发

Question

I need to stop F4's default functionality for ComboBox. While googling for it, I came across in various solutions with previewkeydown of combobox. But for my requirement i cant restrict the previewkeydown event. Any other way to handle this case?. If it is a bug in combobox, any other workaround to get the keydown event for F4 key.

Answer 1

If you want to disable for all ComboBox in your application, then you can do this. Register your KeyDown for ComboBox application wide. You can add this statement in your application start (App.xaml.cs or AppBootStrapper if you are using MVVM)

EventManager.RegisterClassHandler(typeof(ComboBox) ,UIElement.KeyDownEvent ,new KeyEventHandler((sender ,e) =>
{
    var cb = sender as ComboBox;
    if ( cb != null && e.Key == Key.F4 )
        e.Handled = true;   
}));

Be aware, this is not tested. I used similar approach for TextBox move focus on enter.

Answer 2

Although i know this question is old, but i write my tricky solution (as i not found it across web) for someone engaging this problem:

I must say that this behavior is not a bug, It is a common action over all standard drop-down (ComboBox) controls across Windows.

And you can override it simply in WPF by using CommandBinding .

public class MyWindow
{
   private static readonly RoutedCommand DummyEmptyCommand = new RoutedCommand("DummyEmptyCommand", typeof(MyWindow), new InputGestureCollection() { new KeyGesture(Key.F4) });

   public MyWindow()
   {
      MyComboBox.CommandBindings.Add(new CommandBinding(DummyEmptyCommand, (o, e) => 
      { 
         // Do your work here or simply leave it blank to disable F4 common behavior;
      }));
   }
}

In this way, You can implement your own alternative work or just disable the standard common windows behavior.