I have tried in many way but the error message for custom validator is not shown in validation summary but it(ValidationSummary) shows error message for every other type of validator.
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Expt_Custom Validator.aspx.cs" Inherits="Expt_Custom_Validator" %>
<!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 runat="server">
<title>Untitled Page</title>
<script runat="server">
protected void CustomValidator1_ServerValidate(object source, ServerValidateEventArgs args)
{
if (args.Value.Equals("Jagdeep"))
args.IsValid = false;
else
args.IsValid = true;
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Label ID="lblName" runat="server" Text="Enter Your Name"></asp:Label>
<asp:TextBox ID="txtbxName" runat="server"></asp:TextBox>
<asp:CustomValidator ID="CustomValidator1" runat="server"
ErrorMessage="You are Not allowed" Display="None"
onservervalidate="CustomValidator1_ServerValidate"></asp:CustomValidator>
<br />
<asp:Label ID="lblClass" runat="server" Text="Class"></asp:Label>
<asp:TextBox ID="txtClass" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"
ErrorMessage="Please enter Clas" ControlToValidate="txtClass" Display="None"></asp:RequiredFieldValidator>
<br />
<asp:ValidationSummary ID="ValidationSummary1" runat="server" />
<br />
<asp:Button ID="Button1" runat="server" Text="Validate" />
</div>
</form>
</body>
</html>
Custom Validator, when placing in formview will not show its error message after server-side validation (though it has been validated and result is invalid) the mean to fix this in to wrap it by a Update Panel.