title: asp:MaskedEditExtender stops validator working
body: <p>I have a RequiredFieldValidator. The code is below:</p>
  
  <pre><code> &lt;asp:TextBox runat="server" ID="phone" MaxLength="10" Columns="10" 
                              Width="90px"&gt;&lt;/asp:TextBox&gt;
                          &lt;asp:MaskedEditExtender ID="phone_MaskedEditExtender" runat="server" CultureAMPMPlaceholder=""
                              CultureCurrencySymbolPlaceholder="" CultureDateFormat="" CultureDatePlaceholder=""
                              CultureDecimalPlaceholder="" CultureThousandsPlaceholder="" CultureTimePlaceholder=""
                              Enabled="True" TargetControlID="phone" Mask="(999)999-9999" ClearMaskOnLostFocus="False"&gt;
                          &lt;/asp:MaskedEditExtender&gt;
                          &lt;asp:RequiredFieldValidator runat="server" ID="RequiredFieldValidatorPhone" ControlToValidate="phone"
                              ErrorMessage="Phone is required." Display="Dynamic" InitialValue=""  /&gt;
  </code></pre>
  
  <p>If I remove the asp:MaskedEditExtender, the RequiredFieldValidator functions as expected. Otherwise it seems the validator loses its functionality.</p>
  
  <p>Why?
  Thanks.</p>