MVVM is something for me. Databinding your data and behavior so you don’t have any code in your views is for me a nice separation of concepts. However some control’s cannot execute a command for certain events, for example when you select something in a listbox.

Enters InvokeCommandAction, which is a behavior which allows you to invoke a command when a certain event occurs. You can find it beneath Blend’s 4 behaviors:

You can attach this behavior to any control, and then select which command to execute when an event occurs. Let’s use a simple ListBox with strings example:

<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:viewModels="clr-namespace:CommandsAndEvents"
        xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" x:Class="CommandsAndEvents.Window1"
        Title="Window1" Height="300" Width="300">
  <Window.DataContext>
    <viewModels:ListViewModel />
  </Window.DataContext>
    <Grid>
    <ListBox x:Name="listBox" ItemsSource="{Binding Names}" >
    </ListBox>
  </Grid>
</Window>

This window will show a list of names from the following ListViewModel:

public class ListViewModel
{
  public ListViewModel()
  {
    Names = new ObservableCollection<string> { "Jan", "Piet", "Joris", "Corneel" };
    SelectionChangedCommand =
     new RelayCommand("Test", (item) => ShowSelected((string)item)); // string is the type of the selected item
  }

  public ObservableCollection<string> Names { get; set; }

  public ICommand SelectionChangedCommand { get; set; }

  private void ShowSelected(string item)
  {
    MessageBox.Show(item);
  }
}

Now, if I’d like the ListBox to call the SelectionChangedCommand I simply add the following behavior:

Notice that this allows for arguments to be passed to the command, which then allows you access to any property on the control!