Universal App Behavior: press enter on texbox and execute your command

CommandOnEnterPress.cs

    /// <summary>
    ///  <Interactivity:Interaction.Behaviors>
    ///   <MoreBehaviors:CommandOnEnterPress Command="{Binding DoYourCommand}" />
    ///  </Interactivity:Interaction.Behaviors>
    /// </summary>
    [Microsoft.Xaml.Interactivity.TypeConstraint(typeof(TextBox))]
    class CommandOnEnterPress : DependencyObject, IBehavior
    {
        [Microsoft.Xaml.Interactivity.CustomPropertyValueEditor(Microsoft.Xaml.Interactivity.CustomPropertyValueEditor.PropertyBinding)]
        public ICommand Command
        {
            get { return (ICommand)GetValue(CommandProperty); }
            set { SetValue(CommandProperty, value); }
        }
        public static readonly DependencyProperty CommandProperty =
            DependencyProperty.Register("Command", typeof(ICommand), typeof(CommandOnEnterPress), null);

        [Microsoft.Xaml.Interactivity.CustomPropertyValueEditor(Microsoft.Xaml.Interactivity.CustomPropertyValueEditor.PropertyBinding)]
        public object CommandParameter
        {
            get { return (object)GetValue(CommandParameterProperty); }
            set { SetValue(CommandParameterProperty, value); }
        }
        public static readonly DependencyProperty CommandParameterProperty =
            DependencyProperty.Register("CommandParameter", typeof(object), typeof(CommandOnEnterPress), null);

        public Windows.UI.Xaml.DependencyObject AssociatedObject { get; set; }

        public void Attach(Windows.UI.Xaml.DependencyObject associatedObject)
        {
            this.AssociatedObject = associatedObject;
            var textbox = this.AssociatedObject as TextBox;
            textbox.KeyDown += textbox_KeyDown;
        }

        public void Detach()
        {
            var textbox = this.AssociatedObject as TextBox;
            textbox.KeyDown -= textbox_KeyDown;
        }

        void textbox_KeyDown(object sender, Windows.UI.Xaml.Input.KeyRoutedEventArgs e)
        {
            if (e.Key == Windows.System.VirtualKey.Enter
                && this.Command != null)
                this.Command.Execute(this.CommandParameter);
        }
    }