CustomValidator Control

Definition and Usage

The CustomValidator control allows you to write a method to handle the validation of the value entered.

Properties

Property	Description
BackColor	The background color of the CustomValidator control
ClientValidationFunction	Specifies the name of the client-side validation script function to be executed. Note: The script must be in a language that the browser supports, such as VBScript or JScript With VBScript, the function must be in the form: Sub FunctionName (source, arguments) With JScript, the function must be in the form: Function FunctionName (source, arguments)
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
EnableClientScript	A Boolean value that specifies whether client-side validation is enabled or not
Enabled	A Boolean value that specifies whether the validation control is enabled or not
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
id	A unique id for the control
IsValid	A Boolean value that indicates whether the control specified by ControlToValidate is determined to be valid
OnServerValidate	Specifies the name of the server-side validation script function to be executed
runat	Specifies that the control is a server control. Must be set to "server"
Text	The message to display when validation fails

Example 1

In the following example we declare two Label controls, one TextBox control, one CustomValidator control, and one Button control in an .aspx file. The submit() function checks if the page is valid. If it is valid, it returns "The page is valid!" in the "mess" Label control. If it is not valid, it returns "The page is not valid!" in the "mess" Label control. The user() function checks the length of the input value. If the length is <8 or >16 the text "A username must be between 8 and 16 characters!" will appear in the CustomValidator control:

<script runat="server">
sub submit(sender As object,e As EventArgs) 
if Page.IsValid then 
  mess.Text="The page is valid!"
else 
  mess.Text="The page is not valid!"
end if
end sub

Sub user(source As object,args As ServerValidateEventArgs)
if len(args.Value)<8 or len(args.Value)>16 then
  args.IsValid=false
else
  args.IsValid=true
end if
End Sub
</script> 

<html>
<body>

<form runat="server">
  <asp:Label runat="server" Text="Enter a username: " />
  <asp:TextBox id="txt1" runat="server" />
  <asp:CustomValidator
  ControlToValidate="txt1"
  OnServerValidate="user"
  Text="A username must be between 8 and 16 characters!"
  runat="server"/>
  <br />
  <br />
  <asp:Button Text="Submit" OnClick="submit"
  runat="server"/>
  <br />
  <br />
  <asp:Label id="mess" runat="server"/>
</form>

</body>
</html>

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