Материал из .Net Framework эксперт
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Create a new validation control by deriving a new control from BaseValidator
using System;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace myControls
{
public class LengthValidator : BaseValidator
{
int _maximumLength = 0;
public int MaximumLength
{
get { return _maximumLength; }
set { _maximumLength = value; }
}
protected override bool EvaluateIsValid()
{
String value = this.GetControlValidationValue(this.ControlToValidate);
if (value.Length > _maximumLength)
return false;
else
return true;
}
}
}
<%@ Page Language="C#" %>
<%@ Register TagPrefix="custom" Namespace="myControls" %>
<!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>Show Length Validator</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Label
id="lblComments"
Text="Comments:"
AssociatedControlID="txtComments"
Runat="server" />
<br />
<asp:TextBox
id="txtComments"
TextMode="MultiLine"
Columns="30"
Rows="2"
Runat="server" />
<custom:LengthValidator
id="valComments"
ControlToValidate="txtComments"
Text="(Must be less than 10 characters)"
MaximumLength="10"
Runat="server" />
<br /><br />
<asp:Button
id="btnSubmit"
Text="Submit"
Runat="server" />
</div>
</form>
</body>
</html>
