KadroviYshot/FormAuthorization.cs

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;
using System.Data.Entity;

namespace KadroviYshot
{
    public partial class FormAuthorization : Form
    {
        DataBase database = new DataBase();

        public FormAuthorization()
        {
            InitializeComponent();
            StartPosition = FormStartPosition.CenterScreen;
        }

        private void btnEnter_Click(object sender, EventArgs e)
        {
            var loginUser = textBoxLogin.Text;
            var passUser = textBoxPassword.Text;
            SqlDataAdapter adapter = new SqlDataAdapter();
            DataTable table = new DataTable();
            string querystring = $"select IdUser, Login, Password from Users where Login='{loginUser}' and Password='{passUser}'";
            SqlCommand command = new SqlCommand(querystring, database.getConnection());
            adapter.SelectCommand = command;
            adapter.Fill(table);
            if (table.Rows.Count == 1)
            {
                MessageBox.Show("Вы успешно вошли!", "Успешно!", MessageBoxButtons.OK, MessageBoxIcon.Information);
                FormAuthorization authorization = new FormAuthorization();
                this.Hide();
                authorization.ShowDialog();
                this.Show();
            }
            else
                MessageBox.Show("Такого аккаунта не существует!", "Аккаунта не существует!!", MessageBoxButtons.OK, MessageBoxIcon.Warning);
        }

        private void FormAuthorization_Load(object sender, EventArgs e)
        {
            textBoxLogin.MaxLength = 50;
            textBoxPassword.MaxLength = 50;
        }
    }
}