如何实现三层结构中传递数据流？

Question

直接用复杂的类型不行吗？系统自动会帮你作为流发送的：）

Answer 1

做过一个这样的例子.步骤如下:
1.将服务器端对应datasetprovider的options的fetchblobondemand选项设为true,因为false情况下,客户端的clientdataset是不取blob数据的.或者在 false情况下用clientdataset的fetchblob方法取得数据库中的数据.
2.源程序如下(win2000/delphi/ocracle)
procedure writetoblobfield;
var
  tfStream:TFileStream;
  tbStream:TBlobStream;
  nbufsize:integer;
  pbuf:PChar;
begin
  With clientdataset1 do
  begin
    if Active = false then
      Active := true;
    Append;
    try
      tfStream:=TFileStream.Create(FilePath,fmOpenRead);
      nbufsize:=tfStream.Size +1;
      pbuf:=AllocMem(nbufsize);
      tfStream.Read(pbuf^,nbufsize);
      tbStream:=TBlobStream.Create((fieldbyname('TestImage') as TBlobField),bmWrite);
      tbStream.Seek(0,SoFromBeginning);
      tbStream.Write(pbuf^,nbufsize);
    finally
      tfStream.Free ;
      tbStream.Free ;
      post;
      FreeMem(pbuf,nbufsize);
      Active:=False;
    end;
  end;
end;procedure savetoclient;
var
  filebody:tstream;
  tempfile:tmemostream;
begin
  try
   filebody:=clientdataset.createblobstream(Tblobfield,bmread);
   filebody.position:=0;
   tempfile:=tmemostream.create;
   tempfile.loadfromstream(filebody);
   tempfile.savetostream(文件名);
  finally
    tempfile.free;
    filebody.frdd;
  end;
end;
end;