tclientdataset传输数据时出现mismatch in datapacket问题

Question

要把数据库中的图像字段显示到image1中，执行cds1.Data:=cds1.DataRequest(VarArrayOf(['TN_TechPhoto','TechPhoto','00386']));的时候报错，我到事件内跟踪了，执行都正确，返回的olevariant我保存到文件也没问题，就是当DataSetProvider1DataRequest这个事件结束就会出现标题所示错误。
下附完整源码，数据库字段是image类型，经测试取字段数据没问题。unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ADODB, Provider, DB, DBClient, ExtCtrls, StdCtrls, jpeg;type
  TByteArray  = array of byte;
  
  TForm1 = class(TForm)
    Button1: TButton;
    Image1: TImage;
    cds1: TClientDataSet;
    DataSetProvider1: TDataSetProvider;
    ADOQuery1: TADOQuery;
    procedure Button1Click(Sender: TObject);
    function DataSetProvider1DataRequest(Sender: TObject; Input: OLEVariant):
        OLEVariant;
  private
    procedure LoadPicFromDB(fn:string;jpgimg:TImage);
    procedure OleVariantToStream(var Input: OleVariant; Stream: TStream);
    function StreamToOleVariant(Stream: TStream; Count: Integer): OleVariant;
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}procedure TForm1.Button1Click(Sender: TObject);
begin
  cds1.Open;
  cds1.Data:=cds1.DataRequest(VarArrayOf(['TN_TechPhoto','TechPhoto','00386']));
//  ShowMessage('cao');
  if not VarIsNull(cds1.Data) then
    LoadPicFromDB('TechPhoto',Image1)
  else
    Image1.Picture.Graphic:=nil;
end;function TForm1.DataSetProvider1DataRequest(Sender: TObject; Input:
    OLEVariant): OLEVariant;
var
  Ms:TMemoryStream;
  procedure savetofile(pbuf:OleVariant);
  var
    p: Pointer;
    fs:TFileStream;
    nSize:Integer;
  begin
    nSize := VarArrayHighBound(pBuf, 1) - VarArrayLowBound(pBuf, 1) + 1;
    fs := TFileStream.Create('d:\abc', fmCreate or fmOpenWrite);
    try
      p := VarArrayLock(pBuf);
      try
      fs.Seek(0, soFromBeginning);
      fs.WriteBuffer(p^, nSize);
      finally
        VarArrayUnLock(pBuf);
      end;
    finally
      fs.Free;
    end;
  end;
begin
  ms:=TMemoryStream.Create;
  with ADOQuery1 do
  begin
    Close;
    sql.Clear;
    sql.Add('select '+Input[1]+' as tu from '+input[0]+' where FactoryStyle='+QuotedStr(input[2]));
    open;
    if recordcount=1 then
    begin
      TBlobField(FieldByName('tu')).SaveToStream(ms);
      Result:=StreamToOleVariant(ms,ms.Size);
    end
    else
      Result:=NULL;     
  end;
  ms.free;
  savetofile(Result);
end;procedure TForm1.LoadPicFromDB(fn: string; jpgimg: TImage);
var
  Ms:TMemoryStream;
  jpg:Tjpegimage;
  o:OleVariant;
begin
  Ms:=TMemoryStream.Create;
  jpg:=TJPEGImage.Create;
  o:=cds1.Data;
  OleVariantToStream(o,Ms);
  Ms.Position :=0;
  Jpg.LoadFromStream(Ms);
  jpgimg.Picture.Assign(Jpg);
  Ms.Free;
  jpg.free;
end;procedure TForm1.OleVariantToStream(var Input: OleVariant;
  Stream: TStream);
var
  pBuf: Pointer;
begin
  pBuf := VarArrayLock(Input);
  Stream.Write(TByteArray(pBuf^), Length(TByteArray(Input)));
  VarArrayUnlock(Input);
end;function TForm1.StreamToOleVariant(Stream: TStream;
  Count: Integer): OleVariant;
var
  pBuf: Pointer;
begin
  Result:=VarArrayCreate([0,Count-1],varByte);
  pBuf:=VarArrayLock(Result);
  Stream.Position:=0;
  Stream.Read(TByteArray(pBuf^),Length(TByteArray(Result)));
  VarArrayUnlock(Result);
end;end.

Answer 1

var
  o:olevariant;
begin
  ......
  o:=cds1.DataRequest(VarArrayOf(['TN_TechPhoto','TechPhoto','00386']));
  ......
end;