title: String validation in .NET
body: <p>String validation ..</p>
  
  <p>I want to validate a string contains only the following characters :</p>
  
  <ul>
  <li>A-Z</li>
  <li>0-9</li>
  <li>"/"</li>
  <li>"-"</li>
  </ul>
  
  <p>What's the best way to achieve this. I have tried to use a REGEXP but this is returning valid if any of the characters are valid, not if all of the characters are valid.</p>