C# MVC: View with optional ViewModel (data not always present / necessary)

Answer 1

I would suggest that you create a ViewModel and have your View be totally unaware of the fact that data is or is not coming prepopulated from the DB at all.

If you are prepopulating data.. then fill your ViewModel with the necessary data (and disable the inputs that are coming prepopulated)

If you are starting from scratch.. then fill your ViewModel with empty/default data

Either way, all your view does is display the form, and populate default data on the various textboxes and other inputs based upon the passed in ViewModel.

Answer 2

In your View Model:

public class RegistrationViewModel
{
    public bool Invited;

    /*
     * Fields for prepopulating inputs
     */
}

In your View:

<%= Html.TextBox("email", null, Model.Invited ? new { @readonly = "readonly"} : null) %>

or

<%= Html.TextBox("email", null, Model.Invited ? new { @disabled = "disabled"} : null) %>