title: Checking for diacritics with a regular expression
body: <p>Simple problem: an existing project allows me to add additional fields (with additional checks on those fields as regular expressions)  to support custom input forms. And I need to add a new form but cannot change how this project works. This form allows a visitor to enter his first and last name plus initials. So the RegEx <code>^[a-zA-Z.]*$</code> worked just fine for now.<br>
  Then someone noticed that it wouldn't accept diacritic characters as input. A Turkish name like <code>Ömür</code> was not accepted as valid. It needs to be accepted, though.</p>
  
  <p>So I have two options:</p>
  
  <ol>
  <li>Remove the check completely, which would allow users to enter garbage.</li>
  <li>Write a regular expression that would also include diacritic letters but still no digits, spaces or other non-letters.</li>
  </ol>
  
  <p>Since I cannot change the code of the project, I only have these two options. I would prefer option 2 but now wonder what the proper RegEx should be. (The project is written in C# 4.0.)</p>