private void RegisForm_Load(object sender, EventArgs e)
        {
            con = new System.Data.SqlClient.SqlConnection();
            con.ConnectionString = @"Data Source=(localdb)\MSSQLLocalDB;
                                    AttachDbFilename=|DataDirectory|log.mdf;
                                    Integrated Security=True";
            dd();
        }
        public void dd()
        {
            con.Open();
            SqlCommand smd = con.CreateCommand();
            smd.CommandType = CommandType.Text;
            smd.CommandText = "select * from Users";
            smd.ExecuteNonQuery();
            DataTable ds = new DataTable();
            SqlDataAdapter sa = new SqlDataAdapter(smd);
            sa.Fill(ds);
            foreach (DataRow dr in ds.Rows)
            {
                comboBox1.Items.Add(dr["rights"].ToString());
            }
            con.Close();
        }