title: ASP:TextBox or ASP:CheckBoxList, throwing Javascript errors when Requiredfield validator is there
body: <p>I have created a User Control for my SharePoint, which has a simple <code>TextBox</code> and a <code>CheckBoxList</code>. For both of these controls, I have <code>ASP:RequiredFieldValidator</code> and <code>ASP:RegularExpressionValidator</code>. </p>
  
  <p>When I select some item in the <code>CheckBoxList</code> or type some input in the <code>TextBox</code>, I am getting a javascript error in some unknown location. (This is not accepted by my customer.)</p>
  
  <p>Now, when I debug this using FireBug, in the console I see <code>validators[i]</code> is null. It is actually failing in the JS code generated by these validators. </p>
  
  <p>Can some one help me?</p>
  
  <p><strong>Edited:</strong></p>
  
  <pre><code>&lt;asp:TextBox ID="txtNumbers" runat="server" CssClass="Label4" &gt;&lt;/asp:TextBox&gt;
                                      &lt;asp:RegularExpressionValidator ID="RegularExpressionValidatorGPC" runat="server"
                                          ControlToValidate="txtNumbers" ErrorMessage="Only Numbers Accepted "
                                          ValidationExpression="^\d+$"
                                          SetFocusOnError="true"&gt;&lt;/asp:RegularExpressionValidator&gt;
                                      &lt;asp:RequiredFieldValidator ID="RequiredNUMValue" runat="server" ControlToValidate="txtNumbers"
                                          SetFocusOnError="true" ErrorMessage="Please enter a valid number"&gt;&lt;/asp:RequiredFieldValidator&gt;
  </code></pre>
  
  <p>Also, 
  I added required field validators for <code>RadioButtonList</code> (not <code>CheckBoxList</code>).</p>
  
  <pre><code>&lt;asp:RadioButtonList ID="rbtOptions" runat="server" CssClass="Label3"&gt;
                                          &lt;asp:ListItem Text="Option 1" /&gt;
                                          &lt;asp:ListItem Text="Option 2" /&gt;
                                      &lt;/asp:RadioButtonList&gt;
                                      &lt;asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="rbtOptions"
                                          SetFocusOnError="true" ErrorMessage="Please Select a Valid Option"&gt;&lt;/asp:RequiredFieldValidator&gt;
  </code></pre>
  
  <p>When I either input any text in the <code>TextBox</code> or select any option, there is a JavaScript error.</p>