C#(TextBox事件)

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Text;using System.Windows.Forms;namespace Chapter14...{    public partial class Form1 : Form    ...{        public Form1()        ...{            InitializeComponent();            this.button1.Enabled = false;            this.textBox1.Tag = false;            this.textBox2.Tag = false;            this.textBox3.Tag = false;            this.textBox4.Tag = false;