Using RegularExpressionValidator how can I check whether a textBox includes either an at (@) or a hyphen (-)? <p>This is very basic and not thorough validation I know but the textbox needs to accept for example name@email.com as well as 4556-222-44444.</p> <p>I've tried </p> <pre><code>&lt;asp:RegularExpressionValidator Display="Dynamic" runat="server" ControlToValidate="txtAddToBlacklist" ErrorMessage="Invalid" ValidationExpression="^[\-\@]$"&gt;&lt;/asp:RegularExpressionValidator&gt; </code></pre> <p>This attempt included the escaping backslashes to no avail.</p> <p>My logic for using "[-@]" to check for either to be present came from <a href="http://stackoverflow.com/a/4068725/2823680">this answer</a>.</p> <p>I know that the hyphen has to be at the beginning or the end but as it's only two characters, I don't think this is the issue.</p> <p>The ^ and $ are included as that seems to be recommended practice to prevent malicious extras being appended.</p> <p>Must be missing something though so any help is appreciated!</p>