WPF MVVM - Activate ViewModel-command by use of hot keys from MainWindow - wpf

Question

I have an MVVM application in which the MainWindow contains a grid with several views.
In one of the viewmodels there is a command which I can activate by using hot keys in its corresponding view. I can only activate the command when I am placed in the part of the MainWindow that contains the specific view.
The following code works fine, if I only want to be able to activate the command in the specific view:
ComponentView.xaml:
...
<UserControl.InputBindings>
<KeyBinding Gesture="CTRL+U" Command="{Binding Path=UploadCmd}"/>
</UserControl.InputBindings>
</UserControl>
I would like to be able to activate the command by using the hot keys from any part of the MainWindow.
This is my failed attempt to do the keybinding in the MainWindow, so that the command can be activated from anywhere:
MainWindow.xaml:
<Window x:Class="MyProgram.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:view="clr-namespace:MyProgram.View"
xmlns:vm="clr-namespace:MyProgram.ViewModel"
...>
<Grid>
// Grid content
</Grid>
<Window.DataContext>
<vm:ComponentViewModel>
<KeyBinding Gesture="CTRL+U" Command="{Binding Path=UploadCmd}"/>
</vm:ComponentViewModel>
</Window.DataContext>
</Window>
Is it possible to somehow let the application know where the command is directly in the xaml?

Answer 1

Three options I can think of:
You could place your commands in your main window and then use relative source binding from the child views to the command in your main window.
{Binding Path=PathToProperty, RelativeSource={RelativeSource AncestorType={x:Type Window}}}
If you are using an mvvm framework, there is often a way to message / communicate between viewmodels. This is usually not the best solution but can be used in the right circumstance.
Use IOC / Dependecy Injection to create a service that is instantiated as a singleton in your viewmodellocator. Then inject this service implementation into the parent and child viewmodels constructors. Then you can call functions/properties from that service from the parent viewmodel that can be accessed by the child viewmodels. I use this for navigation purposes.
What are you trying to do with those commands?
Hope this helps