C# implements restaurant management system

using System;
using ;
using ;
using ;
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using ;
using ;
using ;
using ;
using ;

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);
   ();
   SqlDataAdapter sda = new SqlDataAdapter("SELECT Password FROM TUser WHERE UserIDName='" + useridname + "'", conn);
   DataTable DT=new DataTable();
   (DT);
   if([0]["Password"].ToString()!=tb_oldpass.Text)
   {
    ("Please re-enter the old password");
    return;
   }
   if (tb_newpassw.Text != tb_newpass.Text)
   {
    ("Please re-enter the password when the two times are different");
    return;
   }
   SqlCommand cmd = new SqlCommand("UPDATE TUser SET Password=@Password WHERE UserIDName='" + useridname + "'", conn);
   ("@Password",,128).Value=tb_newpassw.Text;
   ();
   ("Password modification was successful！(*￣︶￣)y ");
   ();
   ();
  }

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

using System;
using ;
using ;
using ;
using ;
using ;
using ;
using ;
using ;

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

  private void bt_login_Click(object sender, EventArgs e)
  {   
   //Discern whether the user name or password text box is empty   if(tb_username.Text==""||tb_password.Text=="")
   {
    if(tb_username.Text=="")
    {
     ("Username is empty，Please re-enter！(*￣︶￣)y ");
     return;
    }
    if (tb_password.Text == "")
    {
     ("Password is empty，Please re-enter！(*￣︶￣)y ");
     return;
    }
   }

   //Connect the database   SqlConnection conn = new SqlConnection(fm_public.strcon);
   ();
   string selectsql = "SELECT * FROM TUser WHERE UserIDName='" + tb_username.Text + "'";
   SqlDataAdapter sda = new SqlDataAdapter(selectsql, conn);
   DataTable dt = new DataTable();
   (dt);

   //Judge whether the user exists   if ( == 0)
   {
    ("No user");
    return;
   }

   //Discern whether the user name is locked   if (([0]["LockIf"]) == true)
   {
    ("The user has been locked，Please contact the administrator！/(ㄒoㄒ)/~~ ");
    return;
   }

   //Preparation before updating the database   SqlCommand cmd = new SqlCommand();
    = conn;
    = ;

   //Judge whether the password is entered correctly. If the input is incorrect, the "Error Number" + 1. If the "Error Number" is cleared after the login is successfully logged in, the "Error Number" is cleared after the "Error Number" is cleared after the input is incorrect.   if(tb_password.Text!=[0]["Password"].ToString())
   {
    //Number of errors +1     = @"UPDATE TUser SET ErrorTime=ErrorTime+1 WHERE UserIDName=@UserName";
    ("@UserName", , 8);
    ["@UserName"].Value = tb_username.();
    ();

    ("密码错误Please re-enter！/(ㄒoㄒ)/~~ ");
    return;
   }

   // After the above verification, the user name and password are correct, the following code is executed without errors (set the error number is 0)    = "update TUser set ErrorTime=0 where UserIDName=@UserName";
   ("@UserName", , 8);
   ["@UserName"].Value = tb_username.();
   ();
   ();   

   fm_public.LoginSuccess = true;
   //Set user permissions and initialize the relevant parameters of the main interface   if ([0]["Post"].ToString() == "administrator")
   {
    fm_public.userpower = "administrator";
   }
   else
   {
    fm_public.userpower = "waiter";
   }
   fm_public.useridname = [0]["UserIDName"].ToString();
   fm_public.logintime = ();

   ();
  }

  private void bt_esc_Click(object sender, EventArgs e)
  {
   if (("Are you sure to exit the system?", "hint", , ) == )
   {
    ();
   }
  }

  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();
  }
 }
}