CustomValidator
control
The
CustomValidator control allows you to create a validation control with
customized validation logic. The standard validator can not call a user-defined
function. The CustomValidator control calls a user-defined function to perform
validations. The interesting stuff in this control is
that you have ability to validate your input data both from Client side using
JavaScript and Server side by writing your code in code behind file in any of
the .NET supported programming language.
Properties:
These are the
some important properties of the CustomValidator control.
Text
- Text to display for the validator when the validated control is invalid.
BackColor
- The background color of the RequiredFieldValidator control.
ControlToValidate
- The id of the control to validate.
Display
- The display behavior for the validation control. Legal values are:
-None (the control is not displayed. Used to show the error message only
in the ValidationSummary control).
-Static
(the control displays an error message if validation fails. Space is reserved on
the page for the message even if the input passes validation.
-Dynamic
(the control displays an error message if validation fails. Space is not
reserved on the page for the message if the input passes validation.
ErrorMessage - The text to display in the ValidationSummary control when
validation fails. Note: This text will also be displayed in the validation
control if the Text property is not set.
ForeColor
- The foreground color of the control.
For example:
Drag a Label
control, one TextBox control, Button control from the toolbox on the form. The
form looks like this.
Figure1.
Now click on
the source button of the design form to see the .aspx code.
<%@ Page Language="vb" AutoEventWireup="false" CodeBehind="WebForm1.aspx.vb" Inherits="WebApplication13.WebForm1" %>
<!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></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Label ID="Label1" runat="server" Text="Enter a username:
" />
<asp:TextBox id="txt1" runat="server" />
<asp:CustomValidator ID="CustomValidator1"
ControlToValidate="txt1" Text="A
username must be between 6 and 10 characters!"
runat="server" ForeColor="#FF5050"/><br />
<br />
<asp:Button ID="Button1" Text="Submit" runat="server" style="height:
26px"/>
<br />
<br />
</div>
</form>
</body>
</html>
Now double
click on the custom validate control of the design form and add the following
code on the server validate event.
Protected Sub CustomValidator1_ServerValidate(ByVal
source As Object,
ByVal args As
System.Web.UI.WebControls.ServerValidateEventArgs)
Handles CustomValidator1.ServerValidate
If Len(args.Value) < 6
Or Len(args.Value) > 10 Then
args.IsValid =
False
Else
args.IsValid =
True
End If
End Sub
Now save and
run the application and enter three character.
Figure2
Now click on the Button control.
Figure3