datagridview combobox selected items turning empty when to get new data

See more:

combobox

DataGridView

Hi. I have 2 datagridview in one windows form, When I click row from datagridview1, it shows in datagridview2 (Select *from....). Also I have combobox column in datagridview2. My question is, when I select items in combobox, and click to new row in datagridview 1, datagridview2 combobox's is getting empty. it is my code:

private void dataGridView1_CellDoubleClick_1(object sender, DataGridViewCellEventArgs e)
       {
           try
           {
               int id = Convert.ToInt32

    (dataGridView1.Rows[dataGridView1.CurrentRow.Index].Cells["id"].Value);//3

               MySqlConnection start = new MySqlConnection(baglanti);
               MySqlCommand command = start.CreateCommand();
               command.CommandText = "SELECT id, muayine_adi, sabit_qiymet FROM tibbi_xidmetler  WHERE id = '" + id.ToString() + "'";
               start.Open();
               MySqlDataAdapter oxu = new MySqlDataAdapter(command);
               DataTable dt = new DataTable();
               DataSet ds = new DataSet();
               oxu.Fill(dt);
               if (dataGridView2.DataSource != null)
               {
                   DataTable pr = dataGridView2.DataSource as DataTable;
                   bool exists = false;
                   foreach (DataRow dr in pr.Rows)
                   {
                       if (dr.RowState != DataRowState.Deleted)
                       {
                           if (Convert.ToInt32(dr["id"]) == id)
                           {
                               exists = true;
                               break;
                           }
                       }

                   }

                   if (!exists)
                   {
                       pr.Merge(dt);
                       dataGridView2.DataSource = pr;
                   }

               }
               else
               {

                   dataGridView2.DataSource = dt;
               }

               oxuma_hekimler();

               if (dataGridView2.Columns["Sil"] == null)
               {
                   DataGridViewButtonColumn col1 = new DataGridViewButtonColumn();
                   col1.UseColumnTextForButtonValue = true;
                   col1.Text = "Sil";
                   col1.Name = "Sil";
                   dataGridView2.Columns.Add(col1);
               }

               dataGridView2.Columns[0].ReadOnly = true;
               dataGridView2.Columns[1].ReadOnly = true;
               dataGridView2.Columns[2].ReadOnly = true;
               dataGridView2.Columns[3].ReadOnly = false;

               DataGridViewColumn column = dataGridView2.Columns[3];
               column.Width = 200;
               DataGridViewColumn column1 = dataGridView2.Columns[1];
               column1.Width = 250;
               DataGridViewColumn column2 = dataGridView2.Columns[0];
               column2.Width = 40;
               DataGridViewColumn column3 = dataGridView2.Columns[2];
               column3.Width = 60;
               oxuma_sum();


           }
           catch (Exception ex)
           {

               MessageBox.Show(ex.Message);
           }
       }

and it is void to get combobox items

void oxuma_hekimler()
       {
           MySqlConnection baglan = new MySqlConnection(baglanti);
           MySqlCommand command = baglan.CreateCommand();

           command.CommandText = "SELECT hekim_terifi.id, CONCAT (yeni_personal.adi,' ',yeni_personal.soyadi,' (',sobeler.sobe_adi,')') as melumat FROM hekim_terifi INNER JOIN yeni_personal ON yeni_personal.id=hekim_terifi.personal_id INNER JOIN hekim_sobe_tanim ON hekim_sobe_tanim.hekim_id=hekim_terifi.id INNER JOIN sobeler ON sobeler.id=hekim_sobe_tanim.sobe_id";


           baglan.Open();
           MySqlDataAdapter oxu = new MySqlDataAdapter(command);
           DataTable db = new DataTable();
           oxu.Fill(db);

           if (dataGridView2.Columns["combo1"] == null)
           {
               DataGridViewComboBoxColumn col = new DataGridViewComboBoxColumn();
               col.Width = 100;
               col.HeaderText = "Müayinə Həkimi...";
               col.DataSource = db;
               col.Name = "combo1";
               col.FlatStyle = FlatStyle.Standard;
               col.DataPropertyName = "combo1";
               col.DisplayMember = "melumat";
               col.ValueMember = "id";
               dataGridView2.Columns.Add(col);
           }

           int a = Convert.ToInt32(textBox1.Tag);

           foreach (DataGridViewRow row in dataGridView2.Rows)
           {
               (row.Cells[3] as DataGridViewComboBoxCell).Value = a;
           }

           baglan.Close();

       }

How can I solve this? I need help ;(