using System;
using System.Collections.Generic;
using
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace WindowsApplication4 {
    public partial class Form3 : Form {
        public Form3() {
            InitializeComponent();
        }

        private void textBox1_Validating(object sender, CancelEventArgs e) {
            if (this.textBox1.Text == "")
                this.errorProvider1.SetError(this.textBox1, "输入第1个");//指定在那个空间旁边显示提示
            else
                this.errorProvider1.SetError(this.textBox1, null);//清除掉此控件旁边的提示
        }

        private void textBox2_Validating(object sender, CancelEventArgs e) {
            if (this.textBox2.Text == "")
                this.errorProvider1.SetError(this.textBox2, "输入第2个");
            else
                this.errorProvider1.SetError(this.textBox2, null);
        }
    }
}
我不看懂 这具体的要求，运行不通。。。。。。。。。谢谢了

textBox1_Validating(object sender, CancelEventArgs e)函数是正在验证textBox1控件时执行。主要作用是验证textBox1.text内容是不是符合要求。
textBox2_Validating(object sender, CancelEventArgs e)作用同上。