title: Allow certain special characters - Regular expression
body: <p>I want to allow only spaces, hyphens, underscores &amp; commas along with alphabets &amp; numbers. But this is not working as desired.</p>
  
  <pre><code>&lt;asp:RegularExpressionValidator ControlToValidate="txtQuestion"
  Display="dynamic" runat="server" ErrorMessage="*"
  ValidationExpression="^[a-zA-Z0-9-_,\s]$"&gt;&lt;/asp:RegularExpressionValidator&gt;
  
  Character   ShownResult
  -            valid
  _            valid
  ,            valid
  -_           invalid //this should be valid for me
  </code></pre>