I thought this was addressed in Q2 as stated in the following thread http://www.telerik.com/community/forums/aspnet-ajax/ajax/radajaxmanager-and-asp-net-validators.aspx
but i am stilling haveing the same problem,
to repo the problem
I undrestaned that if i set enableclientside... it will work but this is not an option for me.
1. fill out both textboxes (page valid)
2. click the button (all good)
3. remove content of text boxes(one or both),
4. click button and no validation summary
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<telerik:RadAjaxManager ID="RadAjaxManager1" runat="server">
<AjaxSettings>
<telerik:AjaxSetting AjaxControlID="Button1">
<UpdatedControls>
<telerik:AjaxUpdatedControl ControlID="vldSummary2" LoadingPanelID="LoadingPanel3" />
</UpdatedControls>
</telerik:AjaxSetting>
</AjaxSettings>
</telerik:RadAjaxManager>
<telerik:RadAjaxLoadingPanel ID="LoadingPanel3" runat="server">
<img alt='' src='<%= RadAjaxLoadingPanel.GetWebResourceUrl(Page, "Telerik.Web.UI.Skins.Default.Ajax.loading1.gif") %>' />
</telerik:RadAjaxLoadingPanel>
<asp:ValidationSummary ID="vldSummary2" runat="server" />
<table>
<tr>
<td>
<asp:Label ID="Label2" runat="server" Text="first"></asp:Label>
<asp:RequiredFieldValidator ID="vldFirstNameSearc" runat="server" ControlToValidate="txtFirstNameSearch"
ErrorMessage="first required" Display="None">
</asp:RequiredFieldValidator>
</td>
<td>
<asp:Label ID="Label3" runat="server" Text="last"></asp:Label>
<asp:RequiredFieldValidator ID="vldLastNameSearch" runat="server" ControlToValidate="txtLastNameSearch"
ErrorMessage="last requried" Display="None">
</asp:RequiredFieldValidator>
</td>
</tr>
<tr>
<td>
<asp:TextBox ID="txtFirstNameSearch" runat="server" MaxLength="50" Width="85px"></asp:TextBox>
</td>
<td>
<asp:TextBox ID="txtLastNameSearch" runat="server" MaxLength="50" Width="85px"></asp:TextBox>
</td>
</tr>
</table>
<asp:Button ID="Button1" runat="server" Text="Next" />
<telerik:RadMultiPage ID="mpRes" runat="server" SelectedIndex="0">
<telerik:RadPageView ID="pvSearch" runat="server">
</telerik:RadPageView>
</telerik:RadMultiPage>
</form>
</body>
</html>