Linking TextBox Key Presses to a DelegateCommand

I needed to detect the <return> key being pressed in a TextBox. The original technique used a KeyPress event and a small event handler in the code-behind. Since we're using MVVM I wanted to replace the event handler with a DelegateCommand.
This .Net 4 only solution binds the DelegateCommand to the Command property of a KeyBinding.

...
KeyReturnCommand = new DelegateCommand(ReturnKeyPressed);
...
public DelegateCommand KeyReturnCommand { get; set; }
private void ReturnKeyPressed(string text)
{
   MessageBox.Show(text);
}

<TextBox x:Name="SearchText" Width="100" Height="25">
   <TextBox.InputBindings>
       <KeyBinding 
           Command="{Binding KeyReturnCommand}" 
           CommandParameter="{Binding ElementName=SearchText, Path=Text}"  
           Key="Enter"/>
   </TextBox.InputBindings>
</TextBox>