为什么就是提交不了，该怎么改？谢谢指教！
using System;
using System.Collections.Generic;
using
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsExample1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        { }
            private void button1_Click(object sender,EventArgs e)
            {
                if (textBox1.Text=="")
                {
        MessageBox.Show("请输入姓名","提示",MessageBoxButtons.OK,MessageBoxIcon.Exclamation);
        textBox1.Focus();
        return;
                }
                if (comboBox1.Text =="")
                {MessageBox.Show ("请选择出生日期","提示",MessageBoxButtons.OK,MessageBoxIcon.Exclamation);
                comboBox1.Focus();
                    return ;
                }
                if(textBox2.Text=="")
                {
                    MessageBox.Show ("请输入Ｅ－mail地址","提示",MessageBoxButtons.OK ,MessageBoxIcon.Exclamation );
                    textBox2.Focus();
                    return;
                }
                if(textBox2.Text.IndexOf('@')==-1||textBox2.Text.IndexOf('@')==0||textBox2.Text.IndexOf('@')>textBox2.Text.Length -6)
                {
                    MessageBox.Show("E-mail地址有误","提示",MessageBoxButtons.OK,MessageBoxIcon.Exclamation );
                    textBox2.Focus();
                    return;
                }
                MessageBox.Show(textBox1.Text +"你好,计算机网络技术班通过!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information );
                this.Close();
        }
   
    }
}

看看构造函数