title: Get supported characters of a font - in C#
body: <p>I have a third party font with support for japanese characters which I need to use for an application. Whenever a character is not supported by this font, the often seen rectangle ("default character") is drawn. Obviously not all japanese characters are supported, because if I try to draw the translations that our translation office gave us, there are a lot of rectangles.</p>
  
  <p>I need to be notified whenever a not supported character is used, so that I can change the font for this single character (like Word does it) or implement some other reaction to that. </p>
  
  <p>Any ideas? If I could extract a list of unicode characters from the TTF file, then I would be able to check whether a used character is covered by this list. But how can I do so?</p>