title: HTML5 "required" attribute on asp:DropDownList
body: <p>Let's say I have this DDL on my page:</p>
  
  <pre><code>&lt;asp:DropDownList ID="senha" runat="server" required="required" CssClass="form-control"&gt;
      &lt;asp:ListItem Value="" Text="empty" Selected="True"&gt;&lt;/asp:ListItem&gt;
      &lt;asp:ListItem Value="1" Text="test1"&gt;&lt;/asp:ListItem&gt;
      &lt;asp:ListItem Value="2" Text="test2"&gt;&lt;/asp:ListItem&gt;
  &lt;/asp:DropDownList&gt;
  </code></pre>
  
  <p>In this one, the required field will work without problem, if you don't select a value, then it will block the submit.<br>
  But what if the initial value is 0?</p>
  
  <pre><code>&lt;asp:DropDownList ID="senha" runat="server" required="required" CssClass="form-control"&gt;
      &lt;asp:ListItem Value="0" Text="empty" Selected="True"&gt;&lt;/asp:ListItem&gt;
      &lt;asp:ListItem Value="1" Text="test1"&gt;&lt;/asp:ListItem&gt;
      &lt;asp:ListItem Value="2" Text="test2"&gt;&lt;/asp:ListItem&gt;
  &lt;/asp:DropDownList&gt;
  </code></pre>
  
  <p>Now the "required" attribute doesn't work anymore.<br>
  What I want to do is put a pattern in the value to only accept values greater than zero, but I'm not familiar with RegExp, and I don't know if the HTML "pattern" attribute will do what I want.<br>
  Can someone enlighten me?<br>
  I would rather use a solution that uses pure HTML, but if a minimal programming is required, then I don't have choice...</p>