I know the title is a bit confusing but bare with me. (I'm up for suggestions on a new title lol) I'm writing a TemplateEngine that will allow me to use my own markup in text based files. I'm wanting to add controls as plugins as the application matures. Currently i've got a structure like the following:

interface IControl
    string Id
    object Value

class Label : IControl
    string Id
    string Value

class Repeater : IControl
    string Id
    List<IControl> Value

Now you'll see the strange part right away in the Repeater class with the Value property. I was hoping that having the Value type as object in the interface would allow me the flexibility to expand the controls as i go along. The compiler doesn't like this and for good reason i guess.

Does anyone have any suggestions how to accomplish this?

Note: Please don't go into suggesting things like use Spark View Engine for templating. There is a reason i'm creating extra work for myself.