So in C# when I've been creating model classes and lazy loading things, I do something like this:

public int? User_ID { get; set; }

public int? Dept_ID { get; set; }

Then a little farther down in my class I pop in my virtuals like so:

public virtual User User {get; set;}

public virtual Department Dept {get; set;}

How would I do this in Typescript? Something like this?:

User_ID: number;

Dept_ID: number;

User: User;

Dept: Department;

I don't think interfaces is what I want/need...but then again protected doesn't seem correct either. Something tells me I'm missing an obvious answer here.