How to handle purely view-related commands?

Question

There is my WPF window in which I placed an ordinary textbox which I would liked to be focused when Ctrl+F is pressed.

As I would like to keep it MVVM-like as much as possible, I use InputBindings on the window to bind that input event to a Command provided in the ViewModel (is that already breaking MVVM pattern because the whole action is only meant to be part of the view? I guess not, as the Command is an object to bind to).

How can the ViewModel communicate with the view to focus the textbox? I read that this already breaks the MVVM pattern, but sometimes simply is necessary as otherwise impossible. However, setting the focus in the ViewModel itself would be totally breaking the MVVM pattern.

I orginally intended to bind the current focused control in the window to a property of the ViewModel but it is quite difficult to even determine the currently focused element in WPF (that always makes me question if it really is the right way to do so).

Answer 1

After a few days of getting a better grip on all of this, considering and evaluating all options, I finally found a way to work it out. I add a command binding in my window markup:

<Window.InputBindings>
    <KeyBinding Command="{Binding Focus}" CommandParameter="{Binding ElementName=SearchBox}" Gesture="CTRL+F" />
</Window.InputBindings>

The command in my ViewModel (I cut the class down to what matters in this case):

class Overview : Base
{
    public Command.FocusUIElement Focus
    {
        get;
        private set;
    }

    public Overview( )
    {
        this.Focus = new Command.FocusUIElement();
    }
}

And finally the command itself:

class FocusUIElement : ICommand
{
    public event EventHandler CanExecuteChanged;

    public bool CanExecute ( object parameter )
    {
        return true;
    }

    public void Execute ( object parameter )
    {
        System.Windows.UIElement UIElement = ( System.Windows.UIElement ) parameter;
        UIElement.Focus();
    }
}

This might not be straigt MVVM - but stijn's answer has a good point:

So, just stop caring too much about breaking whatever pattern you use and implement a solution instead.

Normally I take care of keeping stuff organised by conventions, especially when I am still new to something, but I do not see anything wrong regarding this.