title: Hidden Field losing its Value on postback
body: <p>I have a ascx page where I am using a hidden field to store the value of a the drop down box as it is generated using a google address finder. My problem is that when I try to store the value directly in the hidden field:</p>
  
  <pre><code>hfDdlVerifyID.Value = ddlVerifySS.SelectedValue;
  </code></pre>
  
  <p>in the event of a button click, the value is stored but on postback is lost again. Whereas, if i try to use Scriptmanager to do it, nothing is stored.</p>
  
  <pre><code>getBuild.AppendLine("$get('" + hfDdlVerifyID.ClientID + "').value = $get('" + ddlVerifySS.ClientID + ").value;");
  
  ScriptManager.RegisterClientScriptBlock(this.Page, this.GetType(), "storeHidden", getBuild.ToString(), true);
  //  Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "storeHidden", getBuild.ToString(), true);
  string test = hfDdlVerifyID.Value.ToString();
  </code></pre>
  
  <p>The ascx page is :</p>
  
  <pre><code>&lt;asp:UpdatePanel ID = ddlUpdate runat="server"&gt;
      &lt;ContentTemplate&gt;
           &lt;asp:Panel ID="pVerify" runat="server"&gt;
               &lt;br /&gt;
               &lt;fieldset&gt;
                   &lt;legend&gt;
                       &lt;asp:Literal ID="lVerify" runat="server" /&gt;
                   &lt;/legend&gt;
                   &lt;asp:CheckBox
                       ID      ="cbVerify"
                       runat   ="server"
                       Text    ="Use the value from the following list, (Uncheck to accept address as it is)."
                       Checked ="true" /&gt;
                   &lt;br /&gt;
                   &lt;asp:DropDownList ID="ddlVerifySS" runat="server"
                       onselectedindexchanged="ddlVerifySS_SelectIndexChange" /&gt;
                   &lt;asp:HiddenField id="hfDdlVerifyID"
                       runat   ="server" /&gt; 
               &lt;/fieldset&gt;
           &lt;/asp:Panel&gt;  
       &lt;/ContentTemplate&gt;
   &lt;/asp:UpdatePanel&gt;
  
   &lt;padrap:Button          ID          ="bVerify"
                           runat       ="server"
                           CssClass    ="btn"
                           OnClick     ="bVerify_Click"
                           Text        ="Verify Address" /&gt;
  
   &lt;asp:Button             ID          ="btnSubSite" 
                           runat       ="server" 
                           text        ="Save"
                           CssCLass    ="btn" 
                           OnClick     ="save_btn_Click_subSite" 
                           onLoad="ddlVerify_Load" /&gt;
  </code></pre>