C# 2.0 generics

I’m playing around with C# 2.0 templates a.k.a. generics. I was really missing them in the past, but finally, they’re there.

However, the specification for C# 2.0 says in §20.1.1: A type parameter cannot be used directly to declare a base class or interface. Why such a restriction? In some cases you may be able to write your own base class, but often you’re not. If I want to extend several existing classes with some additional functionality, I can’t. Of course I could derive from each class and add my desired members, but if it’s functionality I want to add to a few classes, it’s quite impractical.

I’ve written an example. This generic would write to the console, whenever the base control is clicked:

public class ClickedControl : T where T : System.Windows.Forms.Control
{
    public ClickedControl()
    {
        base.Click += new base_Click;
    }

    private void base_Click(object sender, EventArgs e)
    {
        Console.WriteLine(base.Text + " was clicked");
    }
}

In your code you could just write

ClickedControl<System.Windows.Forms.Button> myButton;

Don’t try that home. Well, you may try it, but won’t compile. Unfortunately.