rab/WindowsFormsApp1/Form1.cs

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

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            SqlConnection connection = new SqlConnection("Data Source=CLASS3109;Initial Catalog=hotel;Integrated Security=True");
            connection.Open();

           

            SqlCommand Command = new SqlCommand("select * from users where login=@login AND password=@password", connection);
            Command.Parameters.Add("@login" ,textBox1.Text);
            Command.Parameters.Add("@password", textBox2.Text);

            SqlDataReader read = null;
          

            try
            {
                
                read = Command.ExecuteReader();
                if(read.HasRows){
                    read.Read();
                    if (read["admin"].ToString() == "1") 
                    {

                        Form2 f2 = new Form2();
                        f2.Show();
                        this.Hide();
                    }
                    if (read["manager"].ToString() == "1")
                    {

                        Form3 f3 = new Form3();
                        f3.Show();
                        this.Hide();
                    }

                }


            }

            catch(Exception ex)
            {
                MessageBox.Show(ex.Message.ToString(),"", MessageBoxButtons.OK, MessageBoxIcon.Error );
            }




        }
    }
}