Question

I have the following Interface Declaration:

public interface IBasePresenter
{
    void Run();
    void ShowDialog<T, M>(T t, M m ) where T : UserControl where M : Form,      ISomeInterface<SomeType>;
}

The ShowDialog() is basically a method that will show a modal dialog box to the user. Where ‘T’ is the parent Form and M is the unique dialog to show. M of which there are multiple different types! Hence the reason to choose a generic method!

A couple of ways I think this method could be used:

Presenter.ShowDialog(this, typeof(Form1)); // FigA

Or

Presenter.ShowDialog(this, new Form1()); // FigB

Based upon Fig A or B, what exactly will a sample ShowDialog() method implementation look like?

My questions stems from trying to figure how the generic parameter ‘M’ is instantiated inside of a ShowDialog() method implementation.

Answer 1

You could change the generic method signature as follows:

public void ShowDialog<T>() where T : Form, new() {
    using(var dialog = new T()){
        dialog.ShowDialog();
    }
}

and then the call:

ShowDialog<MyCoolDialog>();

would result in the mtheod creating (not inferring this time ;)) a new instance of the form and showing it in a modal way.