Why does the MailDefinition class require a System.Web.UI.Control?

When creating a MailMessage object by calling the "CreateMailMessage" method on the MailDefinition class, the third parameter is an object of type System.Web.UI.Control.

MailDefinition mail = new MailDefinition();

ListDictionary replacements = new ListDictionary();
replacements.Add("<%myname%>", "John");

mail.BodyFileName = "~/App_Data/Emails/SomeEmail.txt";
mail.From = "me@example.com";
mail.Subject = "Hello";

MailMessage message = mail.CreateMailMessage("example@example.com,", replacements, );

Why is that?
And in the case that I don't have an object of that type, what should I pass instead? Just a new Control object?

Control control = new Control();

UPDATE

I would highly recommend using Razor to build email templates. It has great syntax, works great, and doesn't have any weird dependencies!