requestData.FileName = dl.FileName;

                    fileInfo = client.DownFile(requestData);

                    System.IO.Stream so=new System.IO.FileStream("E:\\迅雷下载\\App_Code\\"+requestData.FileName,System.IO.FileMode.Create);
                    byte[] buffer = new byte[4096];
                    int bytesRead = 0;

                    bytesRead = fileInfo.FileByteStream.Read(buffer, 0, buffer.Length);
                    int osize = (int)fileInfo.size;

                    while (osize > 0)
                    {
                        System.Windows.Forms.Application.DoEvents();
                        so.Write(buffer, 0, bytesRead);
                    }       
                    
                    so.Close();

wcf

 string filePath = System.IO.Path.Combine("E:\\迅雷下载", fileName.FileName);
                System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);

                if (!fileInfo.Exists)
                {
                    throw new System.IO.FileNotFoundException("File not found", fileName.FileName);
                }

                System.IO.FileStream fs = new System.IO.FileStream(filePath, System.IO.FileMode.Open, System.IO.FileAccess.Read);

                result.name = fileName.FileName;
                result.size = fileInfo.Length;
                result.FileByteStream = fs;

给看看这是啥情况