title: RequiredFieldValidator + Button = Postback!
body: <p>i have this markup code:    </p>
  
  <pre><code>&lt;div id="rowIndirizzo" class="form"&gt;
      &lt;label&gt;
          Indirizzo:&lt;/label&gt;
      &lt;asp:DropDownList ID="ddlToponimo" CssClass="indirizzo" runat="server" DataTextField="Toponimo"
          DataValueField="Toponimo"&gt;
      &lt;/asp:DropDownList&gt;
      &lt;asp:TextBox ID="txtStrada" CssClass="textinputStrada" runat="server"&gt;&lt;/asp:TextBox&gt;
      &lt;asp:TextBox ID="txtNumCivico" CssClass="textinputCivico" runat="server"&gt;&lt;/asp:TextBox&gt;
  &lt;/div&gt;
  &lt;div id="divCap" class="form"&gt;
      &lt;label&gt;
          CAP:&lt;/label&gt;
      &lt;asp:TextBox ID="txtCAP" CssClass="textinputCAP" runat="server"&gt;&lt;/asp:TextBox&gt;
  &lt;/div&gt;
  &lt;asp:RequiredFieldValidator ID="rfvToponimo" CssClass="errore2" runat="server" ControlToValidate="ddlToponimo"
      ErrorMessage="Il campo toponimo dell'indirizzo è obbligatorio." Display="Dynamic"
      ValidationGroup="Step4_StruttPrivata1Step" Style="color: Red; display: block !important;"&gt;&lt;/asp:RequiredFieldValidator&gt;
  &lt;asp:RequiredFieldValidator ID="rfvStrada" CssClass="errore2" runat="server" ControlToValidate="txtStrada"
      ErrorMessage="Il campo strada dell'indirizzo è obbligatorio." Display="Dynamic"
      ValidationGroup="Step4_StruttPrivata1Step" Style="color: Red; display: block !important;"&gt;&lt;/asp:RequiredFieldValidator&gt;
  &lt;asp:RequiredFieldValidator ID="rfvNumCivico" CssClass="errore2" runat="server" ControlToValidate="txtNumCivico"
      ErrorMessage="Il campo numero civico dell'indirizzo è obbligatorio." Display="Dynamic"
      ValidationGroup="Step4_StruttPrivata1Step" Style="color: Red; display: block !important;"&gt;&lt;/asp:RequiredFieldValidator&gt;
  &lt;asp:RequiredFieldValidator ID="rfvCAP" CssClass="errore2" runat="server" ControlToValidate="txtCAP"
      ErrorMessage="Il campo CAP è obbligatorio." Display="Dynamic" 
      ValidationGroup="Step4_StruttPrivata1Step" Style="color: Red;
      display: block !important;"&gt;&lt;/asp:RequiredFieldValidator&gt;
  &lt;asp:RegularExpressionValidator ID="revCAP" runat="server" ControlToValidate="txtCAP"
      ValidationExpression="^([0-9]{5})$" ErrorMessage="Il formato del CAP è errato (Es. 01234)"
      Display="Dynamic" ValidationGroup="Step4_StruttPrivata1Step" Style="color: Red;
      display: block !important;" /&gt;
  &lt;asp:Button ID="btnSearchIndirizzo" OnClientClick="return false;" class="buttonnext" runat="server" Text="Inserisci"
      ValidationGroup="Step4_StruttPrivata1Step"&gt;&lt;/asp:Button&gt;
  </code></pre>
  
  <p>I have some control to validate on button click, but i don't want a postback (i can't use input button because dont fire rfv). I have tried with onclientclick event...but nothing.</p>