try
{
    int row = 0;
    for (row = 0; row < dataGridView1.Rows.Count; row++)
    {
        if (dataGridView1.Rows[row].Selected)
        {
            break;
        }
    }
    if (row < dataGridView1.Rows.Count)
    {
        DialogResult result = MessageBox.Show("Kaydı silmek istediğinizden emin misiniz?", "Uyarı", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
        if (result == DialogResult.Yes)
        {
            string silinecekmust = dataGridView1.Rows[row].Cells[0].Value.ToString();
            string connectionString = "Your_Connection_String";
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                string query = "DELETE FROM musteribilgi WHERE musteriNo = @musteriNo";
                using (MySqlCommand command = new MySqlCommand(query, connection))
                {
                    command.Parameters.AddWithValue("@musteriNo", silinecekmust);
                    connection.Open();
                    command.ExecuteNonQuery();
                    connection.Close();
                }
            }
            dataGridView1.Rows.RemoveAt(row);
        }
    }
}
catch (Exception ex)
{
    // Hata durumunda yapılacak işlemler
}