How do I detect when Enter is pressed in a TextBox?

Hi, take a look at this keydown event of my textbox:

private void txtInput_KeyDown(object sender, KeyEventArgs e)
{
if (e.Key == Key.Return)
txtInput.Clear();
}

Simple no? Well, I have wavy red lines beneath both "Key" words. I got that information from the msdn docs, so they, for whatever reason, are giving the wrong syntax.

I just want the textbox to clear when enter is pressed. Could someone help me out?

Thanks

The error is: "KeyEventArgs does not contain a definition for Key."

The second one (for the second "key" word) says "The name key does not exist in the current context".