Command getting null in my Attached application used to convert event to command

I am using mvvm, so I am trying to get less code (or maybe not) in the code. I want to convert KeyDown event to TextBox in Command.I use interactivity dll my Xaml code:

  <TextBox Background="White" Name="txtHigh" AcceptsReturn="False" Height="23" Width="98"  Margin="3" Grid.Column="3" Text="{Binding SelectionHigh, Mode=TwoWay,Converter={StaticResource formatCell}}">
                    <i:Interaction.Triggers>
                        <i:EventTrigger EventName="KeyDown">
                            <commands:EventToCommand Command="{Binding  HighValueChangedCmd}" ></commands:EventToCommand>
                        </i:EventTrigger>
                    </i:Interaction.Triggers>

      

        
        
        
      

    

 and the code to convert the EventToCommand:

  public class EventToCommand : TriggerAction<FrameworkElement>
{
    public ICommand Command
    {
        get { return (ICommand)GetValue(CommandProperty); }
        set { SetValue(CommandProperty, value); }
    }

    public static readonly DependencyProperty CommandProperty =
        DependencyProperty.Register("Command", typeof(ICommand), typeof(EventToCommand), new UIPropertyMetadata(null));


    public object CommandParameter
    {
        get { return (object)GetValue(CommandParameterProperty); }
        set { SetValue(CommandParameterProperty, value); }
    }

    // Using a DependencyProperty as the backing store for CommandParameter.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty CommandParameterProperty =
        DependencyProperty.Register("CommandParameter", typeof(object), typeof(EventToCommand), new UIPropertyMetadata(null));

    protected override void Invoke(object parameter)
    {
        if (Command == null) return;
        if (Command is RoutedCommand)
        {
            var rc = Command as RoutedCommand;
            if (rc.CanExecute(CommandParameter, base.AssociatedObject))
            {
                rc.Execute(CommandParameter, base.AssociatedObject);
            }
        }
        else
        {
            if (Command.CanExecute(CommandParameter))
                Command.Execute(CommandParameter);
        }
    }

}

      

        
        
        
      

    

the problem is in my Invoke method. I get the command = null..Am somehow it doesn't work? and I want to trump the logic in the ExecuteCommand method only if the key is pressed in enter or tab. In the code behind, we can do this using KeyEventArgs.

               KeyEventArgs e;        
               if (e.Key == Key.Enter || e.Key == Key.Tab)
              //logic

      

        
        
        
      

    

how can i achieve this in ExecuteCommand method ???