gridview responding to double click

i have a form which has both textboxes and a gridview. when a staffid is selected from the combo box, the gridview displays all the transactional records about the staff. each staff have got more than one transaction. i want the girdview to display the records in a particular row into their respective textboxes when that row is double - clicked.

i tired this but one particular record keeps on displaying in the text boxes even
if a different row is selected. how do i modify my sql statement to select based on the staffid in the combo box and the tansactionid in the gridview?
pls help me out

private void dgvStaffsalarypayment_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {
           
            SqlConnection conn = new SqlConnection(ConfigurationSettings.AppSettings["ConnectionString"]);
            conn.ConnectionString = "Data Source=MICKY-PC;Initial Catalog=SMS;User ID=sa;Password=mike";
            conn.Open();
            SqlCommand cmd = new SqlCommand();

            string sqlQuery = dgvStaffsalarypayment[0, e.RowIndex].Value.ToString();

            sqlQuery = "select * from tblstaffsalarypaymentdetails where staffid like '" + this.cboStaffid5.Text + "%" + "'";
            cmd.Connection = conn;
            cmd.CommandText = sqlQuery;
            cmd.CommandType = System.Data.CommandType.Text;
            SqlDataReader dr = null;
            dr = cmd.ExecuteReader();
            while (dr.Read())
            {
                cboStaffid5.Text = dr["staffid"].ToString();
                dtpDateofpayment.Text = dr["dateofpayment"].ToString();
                cboPurpose.Text = dr["purpose"].ToString();
                cboYear.Text = dr["years"].ToString();
                cboMonth.Text = dr["months"].ToString();
                txtAmountpaid.Text = dr["amountpaid"].ToString();
                txtRemarks.Text = dr["remarks"].ToString();

            }
            cmd.Dispose();
            

        }

Tags: C#, SQL