为什么dbgrid会无法选中呢，点了一行后dbgrd1.SelectedRows.Count为0,dbgrd1.SelectedIndex为-1，以下是dbgrid的设置:
object dbgrd1: TDBGrid
        Left = 0
        Top = 209
        Width = 567
        Height = 331
        Align = alClient
        DataSource = DataSource2
        Options = [dgTitles, dgIndicator, dgColumnResize, dgColLines, dgRowLines, dgTabs, dgRowSelect, dgConfirmDelete, dgCancelOnExit]
        ReadOnly = True
        TabOrder = 1
        TitleFont.Charset = GB2312_CHARSET
        TitleFont.Color = clWindowText
        TitleFont.Height = -12
        TitleFont.Name = #23435#20307
        TitleFont.Style = []
        OnCellClick = dbgrdVirusCellClick
        OnDrawColumnCell = dbgrdVirusDrawColumnCell
  end