Mega Code Archive
You can associate a custom validation function with the CustomValidator control
<![CDATA[
ControlToValidate: The ID of the form field being validated.
Text: The error message.
ClientValidationFunction: The name of a client-side function.
ServerValidate: This event raised when the CustomValidator performs validation.
<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
void valComments_ServerValidate(Object source, ServerValidateEventArgs args)
{
if (args.Value.Length > 10)
args.IsValid = false;
else
args.IsValid = true;
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>Show CustomValidator</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Label
id="lblComments"
Text="Comments:"
AssociatedControlID="txtComments"
Runat="server" />
<asp:TextBox
id="txtComments"
TextMode="MultiLine"
Columns="30"
Rows="5"
Runat="server" />
<asp:CustomValidator
id="valComments"
ControlToValidate="txtComments"
Text="(Comments must be less than 10 characters)"
OnServerValidate="valComments_ServerValidate"
Runat="server" />
<asp:Button
id="btnSubmit"
Text="Submit"
Runat="server" />
</div>
</form>
</body>
</html>
]]>