Hospital/hospital/authorizationForm.cs

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;
using System.Data.SqlClient;

namespace hospital
{
    public partial class auth : Form
    {
        public static string userID = null;
        SqlConnection sqlConnection = null;
        SqlCommand a = null;
        public static string[] data = new string[0];
        public auth()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            FormCreating.openConnection(ref sqlConnection);
            debugAndTrace.onStart();
            passwordTB.PasswordChar = '●';
            debugAndTrace.writeInFile("Вход в приложение");
        }

        private void signUpBtn_Click(object sender, EventArgs e)
        {
            registrationForm reg = new registrationForm();
            reg.Show();
            this.Hide();
            debugAndTrace.writeInFile("Переход на форму регистрации");

            reg.FormClosing += (obj, args) =>
            {
                this.Show();
            };
        }

        public static string signIn(string login, string password)
        {
            SqlConnection sqlConnection = null;
            FormCreating.openConnection(ref sqlConnection);
            SqlCommand a = null;

            if (login == "admin" && password == "admin")
            {
                return "Добро пожаловать, админ!";
            }
            else
            {
                a = new SqlCommand($"select count(*) from employees where login like {login.GetHashCode()} and password like {password.GetHashCode()} and id_post is null", sqlConnection);
                if (a.ExecuteScalar().ToString().Equals("1"))
                {
                    return "Сначала вам необходимо получить роль!";
                }
                else
                {
                    login = login.Trim();
                    password = password.Trim();
                    a = new SqlCommand($"select count(*) from employees where [login] like N'{login.GetHashCode()}' and [password] like N'{password.GetHashCode()}'", sqlConnection);
                    Array.Resize(ref data, 2);
                    data[0] = "Логин: " + login + "(" + login.GetHashCode() + ")";
                    data[1] = "Пароль: " + password + "(" + password.GetHashCode() + ")";
                    if (a.ExecuteScalar().ToString() == "1")
                    {
                        a = new SqlCommand($"select id_employee from employees where login like N'{login.GetHashCode()}' and password like N'{password.GetHashCode()}'", sqlConnection);
                        userID = a.ExecuteScalar().ToString();
                        return "Успешная авторизация!";
                    }
                    else
                    {
                        return "Такого пользователя не существует\nПроверьте правильность введенных данных, либо зарегистрируйте новый аккаунт";
                    }
                }
            }
        }

        private void signInBtn_Click(object sender, EventArgs e)
        {
            if (loginTB.Text == "admin" && passwordTB.Text == "admin")
            {
                admin Admin = new admin();
                Admin.Show();
                this.Hide();

                Admin.FormClosing += (obj, args) =>
                {
                    this.Show();
                };
            }
            else
            {
                a = new SqlCommand($"select count(*) from employees where login like {loginTB.Text.GetHashCode()} and password like {passwordTB.Text.GetHashCode()} and id_post is null", sqlConnection);
                if (a.ExecuteScalar().ToString().Equals("1"))
                {
                    MessageBox.Show("Сначала вам необходимо получить роль!", "Ошабка", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
                else
                {
                    mainMenu menu = new mainMenu();
                    loginTB.Text = loginTB.Text.Trim();
                    passwordTB.Text = passwordTB.Text.Trim();
                    a = new SqlCommand($"select count(*) from employees where [login] like N'{loginTB.Text.GetHashCode()}' and [password] like N'{passwordTB.Text.GetHashCode()}'", sqlConnection);
                    Array.Resize(ref data, 2);
                    data[0] = "Логин: " + loginTB.Text + "(" + loginTB.Text.GetHashCode() + ")";
                    data[1] = "Пароль: " + passwordTB.Text + "(" + passwordTB.Text.GetHashCode() + ")";
                    if (a.ExecuteScalar().ToString() == "1")
                    {
                        a = new SqlCommand($"select id_employee from employees where login like N'{loginTB.Text.GetHashCode()}' and password like N'{passwordTB.Text.GetHashCode()}'", sqlConnection);
                        userID = a.ExecuteScalar().ToString();
                        debugAndTrace.writeInFile("Авторизация", data);
                        debugAndTrace.writeInFile("Переход на главную форму");
                        menu.Show();
                        this.Hide();
                    }
                    else
                    {
                        MessageBox.Show("Такого пользователя не существует\nПроверьте правильность введенных данных, либо зарегистрируйте новый аккаунт", "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Error);
                        debugAndTrace.writeInFile("Ошибка входа", data);
                    }
                }
            }
        }

        private void auth_FormClosed(object sender, FormClosedEventArgs e)
        {
            Application.Exit();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //mainMenu menu = new mainMenu();
            //menu.Show();
            //this.Hide();
        }

        bool passwordChar = false;

        private void label1_Click(object sender, EventArgs e)
        {
            if (passwordChar)
            {
                passwordTB.PasswordChar = '●';
                passwordChar = !passwordChar;
            }
            else
            {
                passwordTB.PasswordChar = '\0';
                passwordChar = !passwordChar;
            }
        }

        private void label2_Click(object sender, EventArgs e)
        {

        }
    }
}