tclientdataset传输数据时出现mismatch in datapacket问题
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.var o:olevariant;begin ...... o:=cds1.DataRequest(VarArrayOf(['TN_TechPhoto','TechPhoto','00386'])); ......end;