Login

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

namespace beadando_i7vs1c
{
    public partial class LogInForm : Form
    {
        private DataClasses1DataContext _db;

        public LogInForm()
        {
            InitializeComponent();
            _db = new DataClasses1DataContext();
        }

        private void LogInForm_FormClosed(object sender, FormClosedEventArgs e)
        {
            WelcomeForm wf = new WelcomeForm();
            wf.Show();
        }

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

        private void button1_Click(object sender, EventArgs e)
        {
            if (String.IsNullOrWhiteSpace(tbUsername.Text))
            {
                MessageBox.Show("Nem adott meg felhasználónevet.");
                return;
            }
            if (String.IsNullOrWhiteSpace(tbPassword.Text))
            {
                MessageBox.Show("Nem adott meg jelszót.");
                return;
            }
            string username = this.tbUsername.Text;
            string password = this.tbPassword.Text;
            string codedpass = this.EncodePass(password);
            User loginuser = CheckForUserAndPass(username, codedpass);
            if (loginuser == null)
            {
                MessageBox.Show("Nem megfelelő felhasználónevet vagy jelszót adott meg.");
            }
            else
            {
                this.Hide();
                UserWelcome uw = new UserWelcome(loginuser);
                uw.Show();
            }
        }

        private User CheckForUserAndPass(string username, string password)
        {
            try
            {
                User queryUser = (from un in _db.Users
                                  where un.UserName == username && un.Password == password
                                  select un).First();
                return queryUser;
            }
            catch (InvalidOperationException)
            {
                return null;
            }
        }

        private string EncodePass(string password)
        {
            byte[] codedpass = new UTF8Encoding().GetBytes(password);
            byte[] hash = ((HashAlgorithm)CryptoConfig.CreateFromName("MD5")).ComputeHash(codedpass);
            string encoded = BitConverter.ToString(hash).ToLower();
            return encoded;
        }
    }
}