SQLite database is locked in C# : i have 2 quaries but on update `cmd2.ExecuteNonQuery();` it throw exception database is locked 
        if (txt_balance.Text != "")
                        {
                            
                            using ( SQLiteConnection con = new SQLiteConnection(obj.getDbSourceFile))
                            {
                                con.Open();
                                     SQLiteCommand cmd1 = new SQLiteCommand("SELECT [supplier_balance] FROM [s_supplier] where supplier_name='" + comboPurchaseSupplier.Text + "'", con);
                            SQLiteDataReader DR = cmd1.ExecuteReader();
                            // hfcconn.Close();
                            if (DR.HasRows)
                            {
                                if (DR.Read())
                                {
                                    //hfcconn.Open();
                                    using (SQLiteConnection con2 = new SQLiteConnection(obj.getDbSourceFile))
                                    {
                                        SQLiteCommand cmd2 = new SQLiteCommand("update [s_supplier] set supplier_balance=" + (DR.GetInt32(0) + Convert.ToInt32(txt_balance.Text)) + " where supplier_name='" + comboPurchaseSupplier.Text + "'", con2);

                                        con2.Open();
                                        cmd2.ExecuteNonQuery();


                                        DR.Dispose();
                                        // con.Close();
                                    }
                                   

                                }
                            }
                           // con.Close();
                            }
                       
                        }

