自定义控件LengthValidator

1.创建自定义验证控件：新建LengthValidator类并继承BaseValidator

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI.WebControls;

namespace MyControl
{
    public class lengthValidator : BaseValidator
    {
        public int MaximumLength
        {
            get;
            set;
        }
       
        protected override bool EvaluateIsValid()
        {
            string value = this.GetControlValidationValue(this.ControlToValidate);
            if (value.Length > MaximumLength)
                return false;
            else
                return true;
        }
    }
}

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BaseValidator类有两个重要的方法：

1）GetControlValidationValue方法获取被验证控件的值；

2）EvaluateIsValid方法检验控件的值是否有效，有效时返回true，无效返回false。

2.新建LengthValidatorTest页面用LengthValidator控件验证长度

LengthValidator创建后编译一下工具箱最上面即出现LengthValidator，只要把控件拖到要使用的页面即可

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="LengthValidatorTest.aspx.cs" Inherits="WebApplication1.LengthValidatorTest" %>

<%@ Register Assembly="WebApplication1" Namespace="MyControl" TagPrefix="cc1" %>

<!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:TextBox ID="TextBox1" runat="server"></asp:TextBox>
        <cc1:lengthValidator ID="LengthValidator1" runat="server" ControlToValidate ="TextBox1" Display ="Dynamic"  MaximumLength="10" Text ="长度不能大于10个字符"></cc1:lengthValidator>
        <asp:Button ID="Button1" runat="server" Text="提交" onclick="Button1_Click" />
    </div>
    </form>
</body>
</html>

View Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace WebApplication1
{
    public partial class LengthValidatorTest : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            if (Page.IsValid)
            { 
                //....
            }
        }
    }
}

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注：自定义验证控件有错误时并不会阻止页面提交，所以提交数据必须用Page.IsValid检查一下表单是否都通过验证。