WPF - Handle an ApplicationCommand in the ViewModel

Question

I bet this has been answered many times over, but...

For a simple situation where a button on a UserControl has its command property set to something like Find (Appl

Answer 1

The purpose of commands is to decouple the code which generates the order from the code which executes it. Therefore: if you want tight coupling, you should better do it through events:

<UserControl ... x:Class="myclass">
    ...
    <Button Click="myclass_find" .../>
    ...
</UserControl>

---

For loose coupling you need to add a CommandBinding to your UserControl:

<UserControl ... >
    <UserControl.DataContext>
        <local:MyViewModel/>
    </UserControl.DataContext>

    <UserControl.CommandBindings>
        <Binding Path="myFindCommandBindingInMyViewModel"/>
    </UserControl.CommandBindings>
    ...
    <Button Command="ApplicationComamnd.Find" .../>
    ...
</UserControl>

(not sure about the syntax)

Or you can add a CommandBinding to your UserControl's CommandBindings in the constructor, taking the value from the ViewNodel:

partial class MyUserControl : UserControl
{
    public MyUSerControl()
    {
        InitializeComponent();
        CommandBinding findCommandBinding = 
                  ((MyViewModel)this.DataContext).myFindCommandBindingInMyViewModel;
        this.CommandBindings.Add(findCommandBinding);
    }
}