try
            {
               this.dataGridView2.Rows.Clear();
               for (int i = 0; i < dataGridView1.RowCount; i++)
               {
                    bool checkedCell = (bool)dataGridView1.Rows[i].Cells[4].Value;
                    //Boolean nul = (bool)dataGridView1.Rows[i].Cells[4].Value; 
                    //if (nul == null)
                    //{

                        if (checkedCell == true)
                        {
                            string f = dataGridView1.Rows[i].Cells[2].Value.ToString();
                            dataGridView2.Rows.Add(f);
                        }
                    //}
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }