private void All_selected_Click(object sender, EventArgs e)

        {

            for (int i = ; i < this.DataGridViewProduct.Rows.Count; i++)

            {

                if (DataGridViewProduct.Rows[i].Cells["Check"].EditedFormattedValue.ToString().ToLower()=="false")

                {

                    DataGridViewProduct.Rows[i].Cells["Check"].Value = "True";

                }

            }

        }

 public void AllCancel()

        {

            foreach (DataGridViewRow row in DataGridViewProduct.Rows)

            {

                row.Selected = false;

            }

        }