Question

I have a program that needs to navigate through a series of screens in a given order. What I’d like to do is to manage this centrally, using something analogous to a class factory, where I send a request for the next form, and it instantiates and returns the next form. I have the following, however, this will instantiate all the forms immediately:

private List<Form> screens = new List<Form>() { new Form1(), new Form2(), … };
private Form currentForm;
private int currentPos;

public Form Next()
{            
    currentForm = screens[++currentPos];
    return currentForm;
}

Is there a way to defer instantiation until the actual request is made? For example:

private List<Form> screens = new List<Form>() { Form1,Form2, …};
private Form currentFrm;
private int currentPos;

public Form Next()
{            
    currentForm = new screens[++currentPos];
    return currentFrm;
}

(this won’t compile)

Answer 1

One way to do that is to store types in your list and use Activator.CreateInstance() to dynamically create the form instances:

private Type[] screenTypes = new Type[] {
    typeof(Form1),
    typeof(Form2),
    ...
};

private Form currentForm;
private int currentPos;

public Form Next()
{            
    currentForm = (Form) Activator.CreateInstance(screenTypes[++currentPos]);
    return currentForm;
}