[WPF] Prevent the user from pasting an image in a RichTextBox

WPF’s RichTextBox control is quite powerful, and very handy if you need to accept rich text input. However, one of its features can become an issue: the user can paste an image. Depending on what you intend to do with the text entered by the user, you might not want that. When I googled for a way to prevent that, the only solutions I found suggested to intercept the Ctrl-V keystroke, and swallow the event if the clipboard contains an image.