I created a very simple test program to try to understand KeyBinding in WPF, but it’s not working the way I expect it, in fact it doesn’t work at all in most of the cases. Maybe you can point out what I’m doing wrong or what is not supposed to work.

I have a DelegateCommand or RelayCommand class (or whatever it is called in your case), that is implementing ICommand and takes an Action, that is supposed to be called, when the ICommand is executed.

Then I created a simple view model that only contains three commands (for the sake of simplicity my example code does only show one of the commands, the other commands are for Ctrl-B and Ctrl+C.

Public Class MainViewModel
    Inherits ViewModelBase

    Private _keyBindingCommandCtrlA As ICommand = New DelegateCommand(AddressOf Me.KeyBindingCtrlAFired)

    Private Sub KeyBindingCtrlAFired(obj As Object)
        MessageBox.Show("Ctrl+A")
    End Sub

    Public ReadOnly Property KeyBindingCommandCtrlA As ICommand
        Get
            Return _keyBindingCommandCtrlA
        End Get
    End Property

End Class

Then I created two custom controls “Level1” and “Level2”.

“Level2” just contains a defined KeyBinding for Ctrl+C like this:

<UserControl.InputBindings>
    <KeyBinding Key="C" Modifiers="Ctrl" Command="{Binding KeyBindingCommandCtrlC}" />
</UserControl.InputBindings>

“Level1” contains a defined KeyBinding for Ctrl+B and the “Level2” control (not shown in the example):

<UserControl.InputBindings>
    <KeyBinding Key="B" Modifiers="Ctrl" Command="{Binding KeyBindingCommandCtrlB}" />
</UserControl.InputBindings>

My main window contains a reference to the view model, a KeyBinding for Ctrl+A and it contains the “Level1” control (not shown in the example).

<Window.DataContext>
    <local:MainViewModel />
</Window.DataContext>

<Window.InputBindings>
    <KeyBinding Key="A" Modifiers="Ctrl" Command="{Binding KeyBindingCommandCtrlA}" />
</Window.InputBindings>

When I run this example program I would have expected that all three KeyBindings work, so, when I press Ctrl+A, Ctrl+B or Ctrl+C, I’d see a message box telling me Ctrl+A, Ctrl+B or Ctrl+C.
But only Ctrl+A works. when pressing Ctrl+B or Ctrl+C nothing happens.

Then I tried something else. I removed the KeyBindings in “Level1” and “Level2” and added a KeyBinding for Ctrl+B directly to the “Level1” control in my main window like this:

<local:Level1Control>
    <local:Level1Control.InputBindings>
        <KeyBinding Key="B" Modifiers="Ctrl" Command="{Binding KeyBindingCommandCtrlB}" />
    </local:Level1Control.InputBindings>
</local:Level1Control>

But that didn’t help either, when pressing Ctrl+B nothing happens.

So, how do I get KeyBindings to work, when they’re not defined at Window level?