protected override void OnCellValidating(DataGridViewCellValidatingEventArgs e)
        {
                    string c = dgsele.CurrentRow.Cells["编号"].Value.ToString();
                    if (c != "")
                    {
                        MessageBox.Show(" 找不到对应编号!" , "", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
                        e.Cancel = true;

                        //目前我只能这样清空单元格

                        SendKeys.Send("{BACKSPACE}");

                    }
        }

//我很奇怪,为什么用下面的代码都无法清空

this.CurrentCell.Value=""; 
this[e.ColumnIndex, e.RowIndex].Value = "";