title: Matching an (easy??) regular expression using C#'s regex
body: <p>Ok sorry this might seem like a dumb question but I cannot figure this thing out :</p>
  
  <p>I am trying to parse a string and simply want to check whether it only contains the following characters : '0123456789dD+ '</p>
  
  <p>I have tried many things but just can't get to figure out the right regex to use!</p>
  
  <pre><code>
    Regex oReg = new Regex(@"[\d dD+]+");
    oReg.IsMatch("e4");
  </code></pre>
  
  <p>will return true even though e is not allowed...
  I've tried many strings, including Regex("[1234567890 dD+]+")...</p>
  
  <p>It always works on <a href="http://regexpal.com/" rel="nofollow noreferrer">Regex Pal</a> but not in C#...</p>
  
  <p>Please advise and again i apologize this seems like a very silly question</p>