title: Regex c# only positive numbers
body: <p>I am looking for a regular expression that validates only positive numbers(integers):</p>
  
  <p>0-999 and first number not 0. </p>
  
  <p>My example not work:</p>
  
  <pre><code>string pattern = @"^\d+$";
  </code></pre>
  
  <p>How decided positive numbers pattern?</p>