关于blobstream，怎么老出错！！！

Question

procedure TForm1.Button2Click(Sender: TObject);
var
  a1:TBlobStream;
  aq:Tbitmap;
begin
  aq:=tbitmap.Create;   with adoquery1 do
    begin
       close;
       sql.clear;
       sql.Add('select * from one');
       open;
       a1:=TBlobStream.Create(TBlobField(FieldByName('tinfo')),bmRead);
//一运行到上面这行出错       
aq.LoadFromStream(a1);
       Image1.Picture.Assign(aq);
       edit1.Text:=fieldbyname('tname').AsString;
      close;
    end;
  a1.Free;
  aq.Free;
end;这是什么问题 出错提示 "invalid class typecast"怪了 我入库都好好的

Answer 1

var
  PictureStream:TADOBlobStream;
  jpg:TJPEGImage;
begin
  PictureStream:=TADOBlobStream.Create(ADOTable1.FieldByName('照片') as TBlobField,BMRead);
  jpg:=TJPEGImage.Create;
  jpg.LoadFromStream(PictureStream);
  Image1.Picture.BitMap.Assign(jpg);
  PictureStream.Free;
  jpg.Free;
end;