title: Required Field Validator not Working For DropDownList
body: <p>Why is the validator not working here. It's working fine for other textbox controls though.
  There is no error. Its just does the postback.</p>
  
  <pre><code>&lt;asp:DropDownList Id="ddlCustomer" runat="server" AppendDataBoundItems="true"
   DataTextField="customername" DataValueField="customerid"&gt;
  &lt;asp:ListItem Text="--Select--" Value="0"&gt;&lt;/asp:ListItem&gt; 
  &lt;asp:ListItem Text=" &lt; Add New &gt; " Value="0"&gt;&lt;/asp:ListItem&gt;
  &lt;/asp:DropDownList&gt;
  
  &lt;asp:RequiredFieldValidator runat="server" ControlToValidate="ddlCustomer"
  cssclass="required" display="dynamic" errormessage="*" setfocusonerror="true"
  initialvalue="--Select--"&gt;&lt;/asp:RequiredFieldValidator&gt;
  </code></pre>