How to avoid duplication when inserting in C#

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C#

Hi friends first I am stuck in this problem I could not solve it and I already published here brief I will copy the status description "I will explain the state after I will give you my need
I have a DataGridView with a check box I check the rows after I click the "save" button and normally the rows I check that they will have to be inserted in both the other table but I find that Just a line that was inserted twice
The second problem is that I want the rows I inserted that I want the most to see when I click the search button because they are already assigned in the table
You will find the two interfaces that process the "
I hope I have described my condition well and thank you in advance

What I have tried:

//script search button
private void button4_Click(object sender, EventArgs e)
        {
            dataGridView2.Rows.Clear();
            Program.cmd.CommandText = "select * from bon_reception_marche where Date_reception between '" + dateTimePicker1.Value.Date + "' and '" + dateTimePicker2.Value.Date + "' and Id_marche in (select TOP 1 Id_marche from marche where Num_marche = '" + textBox1.Text + "')";
            Program.dr = Program.cmd.ExecuteReader();
            while (Program.dr.Read())
            {
                dataGridView2.Rows.Add(Program.dr[0], Program.dr[2], Program.dr[3], Program.dr[5], Program.dr[6], Program.dr[7], Program.dr[8], Program.dr[9], Program.dr[10], Program.dr[11], Program.dr[12]);
            }
            Program.dr.Close();
        }
        //script click datagridview
        private void dataGridView2_CellClick(object sender, DataGridViewCellEventArgs e)
        {
            if (e.ColumnIndex == 11/*myColumn*/ && e.RowIndex >= 0 /*myRow*/)
            {
                button1.Enabled = true;
            }
        }
        //script button save :
        private void button1_Click(object sender, EventArgs e)
        {
            int colIndex = dataGridView2.Columns["CheckBox"].Index;
            try
            {
                var rows = dataGridView2.Rows
                .Cast<DataGridViewRow>()
                .Where(row => row.Cells[colIndex].Value != null)
                .Where(row => (bool)row.Cells[colIndex].Value)
                .ToList();
                foreach (DataGridViewRow row in rows)
                    insertRowData(row);
                MessageBox.Show("c'est ajouté avec succés");
            }
            catch (FormatException)
            {
                MessageBox.Show("Only input numbers into the table!",
                "Only Numbers", MessageBoxButtons.OK);
            }
            catch (Exception)
            {
                MessageBox.Show("There was an error while saving!",
                "Error", MessageBoxButtons.OK);
            }
        }
        private void insertRowData(DataGridViewRow row)
        {
            double montantValue = Convert.ToDouble(row.Cells["Column7"].Value);
            int id_br_value = Convert.ToInt32(row.Cells["Column11"].Value);
            string check;
            if (checkBox1.Checked == true)
            {
                check = "O";
            }
            else
            {
                check = "N";
            }
            Program.cmd.Parameters.Clear();
            Program.cmd.CommandText = "insert into attachement_marche (Id_bon_reception_marche,Id_marche,Num_attachement,Date_debut,Date_fin,Flag_dernier,Montant,User_create,Date_create) values ( " + id_br_value + ",(select TOP 1 Id_marche from marche where Num_marche = '" + textBox1.Text + "'),'" + textBox3.Text + "','" + dateTimePicker1.Value.Date + "','" + dateTimePicker1.Value.Date + "','" + check + "'," + montantValue + ",'" + values.username + "','" + DateTime.Now.Date + "')";
            Program.cmd.ExecuteNonQuery();
        }