DataGridView取得滑鼠所指到的成員index，並選擇它

剛好有用到 記錄一下

private void AlertDataGrid_MouseClick(object sender, MouseEventArgs e)
{
//選取datagridview的職
DataGridView.HitTestInfo hit = AlertDataGrid.HitTest(e.X, e.Y);
int index = hit.RowIndex;
if (e.Button == MouseButtons.Right && index != -1)
{
AlertDataGrid.CurrentCell = AlertDataGrid.Rows[index].Cells[0];
//跳出選單
Menu.Show(Cursor.Position.X, Cursor.Position.Y);
}
}