C#实现餐厅管理系统

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Data.SqlClient;

namespace FoodManage
{
 public partial class fm_change_password : Form
 {
  public fm_change_password()
  {
   InitializeComponent();
  }

  public string useridname = "";

  private void bt_ok_Click(object sender, EventArgs e)
  {
   SqlConnection conn=new SqlConnection(fm_public.strcon);
   conn.Open();
   SqlDataAdapter sda = new SqlDataAdapter("SELECT Password FROM TUser WHERE UserIDName='" + useridname + "'", conn);
   DataTable DT=new DataTable();
   sda.Fill(DT);
   if(DT.Rows[0]["Password"].ToString()!=tb_oldpass.Text)
   {
    MessageBox.Show("旧密码错误请重新输入");
    return;
   }
   if (tb_newpassw.Text != tb_newpass.Text)
   {
    MessageBox.Show("两次密码不相同请重新输入");
    return;
   }
   SqlCommand cmd = new SqlCommand("UPDATE TUser SET Password=@Password WHERE UserIDName='" + useridname + "'", conn);
   cmd.Parameters.Add("@Password",SqlDbType.VarChar,128).Value=tb_newpassw.Text;
   cmd.ExecuteNonQuery();
   MessageBox.Show("修改密码成功！(*￣?幔?)y ");
   conn.Close();
   this.Close();
  }

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

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

namespace FoodManage
{
 public partial class fm_login : Form
 {
  public fm_login()
  {
   InitializeComponent();
  }

  private void bt_login_Click(object sender, EventArgs e)
  {   
   //判断用户名或密码文本框是否为空
   if(tb_username.Text==""||tb_password.Text=="")
   {
    if(tb_username.Text=="")
    {
     MessageBox.Show("用户名为空，请重新输入！(*￣?幔?)y ");
     return;
    }
    if (tb_password.Text == "")
    {
     MessageBox.Show("密码为空，请重新输入！(*￣?幔?)y ");
     return;
    }
   }

   //连接数据库
   SqlConnection conn = new SqlConnection(fm_public.strcon);
   conn.Open();
   string selectsql = "SELECT * FROM TUser WHERE UserIDName='" + tb_username.Text + "'";
   SqlDataAdapter sda = new SqlDataAdapter(selectsql, conn);
   DataTable dt = new DataTable();
   sda.Fill(dt);

   //判断用户是否存在
   if (dt.Rows.Count == 0)
   {
    MessageBox.Show("无该用户");
    return;
   }

   //判断用户名是否被锁定
   if (Convert.ToBoolean(dt.Rows[0]["LockIf"]) == true)
   {
    MessageBox.Show("该用户已经被锁定，请联系管理员！/(ㄒoㄒ)/~~ ");
    return;
   }

   //更新数据库前的准备
   SqlCommand cmd = new SqlCommand();
   cmd.Connection = conn;
   cmd.CommandType = CommandType.Text;

   //判断输入密码是否正确，输入错误则“错误次数”+1，成功登录则“错误次数”清零
   if(tb_password.Text!=dt.Rows[0]["Password"].ToString())
   {
    //错误次数+1
    cmd.CommandText = @"UPDATE TUser SET ErrorTime=ErrorTime+1 WHERE UserIDName=@UserName";
    cmd.Parameters.Add("@UserName", SqlDbType.VarChar, 8);
    cmd.Parameters["@UserName"].Value = tb_username.Text.Trim();
    cmd.ExecuteNonQuery();

    MessageBox.Show("密码错误请重新输入！/(ㄒoㄒ)/~~ ");
    return;
   }

   //经过以上验证用户名密码无错执行以下代码（设置错误次数为0）
   cmd.CommandText = "update TUser set ErrorTime=0 where UserIDName=@UserName";
   cmd.Parameters.Add("@UserName", SqlDbType.VarChar, 8);
   cmd.Parameters["@UserName"].Value = tb_username.Text.Trim();
   cmd.ExecuteNonQuery();
   conn.Close();   

   fm_public.LoginSuccess = true;
   //设置用户权限以及初始化主界面的相关参数
   if (dt.Rows[0]["Post"].ToString() == "管理员")
   {
    fm_public.userpower = "管理员";
   }
   else
   {
    fm_public.userpower = "服务员";
   }
   fm_public.useridname = dt.Rows[0]["UserIDName"].ToString();
   fm_public.logintime = DateTime.Now.ToShortDateString();

   this.Close();
  }

  private void bt_esc_Click(object sender, EventArgs e)
  {
   if (MessageBox.Show("确定退出系统吗？", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Asterisk) == DialogResult.OK)
   {
    Application.Exit();
   }
  }

  private void fm_login_Activated(object sender, EventArgs e)
  {
   tb_username.Focus();
  }

  private void fm_login_Load(object sender, EventArgs e)
  {
   fm_start fm_starts = new fm_start();
   fm_starts.ShowDialog();
  }
 }
}