学习了用VS2012制作了程序的登陆界面

代码块

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace shaochao2017270402
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.comboBox1.SelectedIndex = 1;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (this.textBox2.Text == "" || this.textBox1.Text == "")
            {
                MessageBox.Show("用户名密码不能为空", "提示", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            else
            {
                if (this.comboBox1.SelectedItem.ToString() == "收银员")
                {
                    if (this.textBox1.Text == "111111" && this.textBox1.Text == "111111"
                        || this.textBox1.Text == "123456" && this.textBox2.Text == "123456")
                    {
                        //MessageBox.Show("收银员登录成功");
                        this.Hide();
                        Form2 fm2 = new Form2();
                        fm2.userName = this.textBox1.Text.ToString();
                        //fm2.MdiParent = this;
                        fm2.Show();
                    }
                    else
                    {
                        MessageBox.Show("用户名或者密码错误", "提示", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    }
                }
                else if (this.comboBox1.SelectedItem.ToString() == "库管员")
                {
                    if (this.textBox1.Text == "1" && this.textBox2.Text == "1")
                    {
                        //MessageBox.Show("库管员登录成功");
                        this.Hide();
                        Form3 fm2 = new Form3();
                        fm2.userName = this.textBox1.Text.ToString();
                        //fm2.MdiParent = this;
                        fm2.Show();
                        
                    }
                    else
                    {
                        MessageBox.Show("用户名或者密码错误", "提示", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    }
                }
                
            }
        }

        private void linkLabel1_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
        {
            MessageBox.Show("请联系管理员", "提示", MessageBoxButtons.OK);
        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == (char)Keys.Enter)
            {
                SendKeys.Send("{tab}");
            }
        }

        private void textBox2_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == (char)Keys.Enter)
            {
                this.button1_Click(sender, e);
            }
        }

        private void textBox1_Enter(object sender, EventArgs e)
        {
            ((TextBox)sender).SelectAll();
        }

        private void textBox2_Enter(object sender, EventArgs e)
        {
            ((TextBox)sender).SelectAll();
        }
    }
}