How Do You Communicate Service Layer Messages/Errors to Higher Layers Using MVP?

I'm currently writing an ASP.Net app from the UI down. I'm implementing an MVP architecture because I'm sick of Winforms and wanted something that had a better separation of concerns.

So with MVP, the Presenter handles events raised by the View. Here's some code that I have in place to deal with the creation of users:

public class CreateMemberPresenter
{
    private ICreateMemberView view;
    private IMemberTasks tasks;

    public CreateMemberPresenter(ICreateMemberView view) 
        : this(view, new StubMemberTasks())
    {
    }

    public CreateMemberPresenter(ICreateMemberView view, IMemberTasks tasks)
    {
        this.view = view;
        this.tasks = tasks;

        HookupEventHandlersTo(view);
    }

    private void HookupEventHandlersTo(ICreateMemberView view)
    {
        view.CreateMember += delegate { CreateMember(); };
    }

    private void CreateMember()
    {
        if (!view.IsValid)
            return;

        try
        {
            int newUserId;
            tasks.CreateMember(view.NewMember, out newUserId);
            view.NewUserCode = newUserId;
            view.Notify(new NotificationDTO() { Type = NotificationType.Success });
        }
        catch(Exception e)
        {
            this.LogA().Message(string.Format("Error Creating User: {0}", e.Message));
            view.Notify(new NotificationDTO() { Type = NotificationType.Failure, Message = "There was an error creating a new member" });
        }
    }
}

I have my main form validation done using the built in .Net Validation Controls, but now I need to verify that the data sufficiently satisfies the criteria for the Service Layer.

Let's say the following Service Layer messages can show up:

• E-mail account already exists (failure)
• Refering user entered does not exist (failure)
• Password length exceeds datastore allowed length (failure)
• Member created successfully (success)