Работа с БД пользователей

command.CommandText = "select * from csharp where user = '" + textBox1.Text + "' AND password = '" + maskedTextBox1.Text + "'";

if (abc == "")
{
//сообщение об отсутсвии юзера
}

            //Подключились к бд
            SqlConnection myConnection = new SqlConnection("server=localhost;uid=sa;pwd=;database=new_db");
            SqlCommand myCommand = new SqlCommand("select  * from employee", myConnection);
            DataSet ds = new DataSet();
            ds.DataSetName = "employee";
            
            Source = new DataView(ds.Tables["employee"]);
            MyDataGrid.DataSource = Source;
            MyDataGrid.DataBind();

 Source = new DataView(ds.Tables["employee"]);
            MyDataGrid.DataSource = Source;
            MyDataGrid.DataBind();

dataGridView1.Columns.Clear();
            dataGridView1.DataSource = myDataSet.Tables[0].DefaultView;

 MySqlConnection myConnection1 = new MySqlConnection("Database=gb_testmsg;Data Source=mysql65.1gb.ru;User Id=gb_testmsg;Password=****");
            string sSQL = "SELECT mail_id,CONCAT_WS(' ',user_name,user_surname),mail_sender,mail_subject,mail_message,user_photo FROM mail_db INNER JOIN users_db ON mail_db.mail_sender=users_db.user_id Where mail_status=0 AND mail_type=1 AND mail_recipient='" + myUserId + "'";
            MySqlCommand myCommand1 = new MySqlCommand(sSQL, myConnection1);
            myConnection1.Open();
            MySqlDataAdapter AdapterP = new MySqlDataAdapter();
            AdapterP.SelectCommand = myCommand1;
            DataSet myDataSet = new DataSet();
            AdapterP.Fill(myDataSet);
            dataGridView1.Columns.Clear();
            dataGridView1.DataSource = myDataSet.Tables[0].DefaultView;
            dataGridView1.Columns[0].Visible = false;
            dataGridView1.Columns[2].Visible = false;
            dataGridView1.Columns[4].Width = 150;
            dataGridView1.Columns[5].Visible = false;
            dataGridView1.Columns.Add(new DataGridViewCheckBoxColumn());
            dataGridView1.Columns[6].Width = 20;
 
            myConnection1.Close();