konkyrs/konkurs/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.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace konkurs
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button3_Click(object sender, EventArgs e)
        {

        }
        public string constring = "Data Source=DESKTOP-Q8BTJMH;Initial Catalog=konkurs;Integrated Security=True";
        private void button2_Click(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection(constring);
            SqlDataReader sqlReader = null;
            con.Open();
            SqlCommand command = new SqlCommand("Select * FROM [dbo].[Users] WHERE login =  @login  AND password = @password", con);
            command.Parameters.Add("@login", textBox1.Text);
            command.Parameters.Add("@password", textBox2.Text);
            try
            {
                sqlReader = command.ExecuteReader();
                while (sqlReader.Read())
                {

                    Form2 fr2 = new Form2();
                    fr2.Show();
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString(), ex.Source.ToString(), MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            finally
            {
                if (sqlReader != null)
                    sqlReader.Close();
            }
        }
    
            
        }
    }