Migration from the MVVM Light Toolkit to the Community MVVM Toolkit

Question

I work on the migration of our WPF project that uses the MVVM pattern from the MVVM Light Toolkit to the Community MVVM Toolkit. But I don't understand how to port some message classes.

public class ListRequestMessage : NotificationMessageAction<IEnumerable<SelectableElement>>
{
    public NewTargetCollectionRequestMessage(object sender, string notification, Action<IEnumerable<SelectableElement>> callbackAction)
        : base(sender, notification, callbackAction)
    {
    }
}

And in my code I use the ListRequestMessage.Sender and ListRequestMessage.Notification properties.

Also, there is another class:

public class FilterItemsMessage : GenericMessage<FilterItem>
{
    public FilterItemsMessage(FilterItem filterItem)
        : base(filterItem)
    {
    }
}

And I use the FilterItemsMessage.Content property in my code.

GenericMessage class can be changed to ValueChangedMessage class. But I don't see any classes to use instead of the NotificationMessageAction class with available Sender and Notification.