How send memorystream data using weba

private void btn_Send_PDF_Click(object sender, EventArgs e)
       {
           int Patient_Master_Id = Convert.ToInt16(txt_Patient_No.Tag);
           XtraReport report = new XtraReport();
           string[,] paramsArray = new string[,]
               {
                   {"@Patient_Master_Id", Patient_Master_Id.ToString()},
                   {"@Test_Group_Id",TestGroupId.ToString()},
                   {"@stSearh",""},
               };
           report = new Print_Test_Patient_Report();
           report.DataSource = _Master_Repository.Run_Dynamic_SP("Print_Patient_Test_Report", paramsArray);
           MemoryStream mem = new MemoryStream();
           report.ExportToPdf(mem);
           mem.Seek(0, System.IO.SeekOrigin.Begin);

           HttpClient client = new HttpClient();
           client.DefaultRequestHeaders.Accept.Clear();
           client.BaseAddress = new Uri("http://localhost:4079/");
           client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
           Laboratory_Reports LR = new Laboratory_Reports();
           LR.Laboratory_Id = 0;
           LR.Register_No = "Reg001"; ;
           LR.Laboratory_Name = "Rsoft Laboratory";
           LR.Patient_No = txt_Patient_No.Text;
           LR.Patient_Name = txt_Name.Text;
           LR.Password = "007";
           LR.Report_Url = "";
           LR.Report_Extension = ".pdf";
           LR.Upload_Date = DateTime.Now;

           StreamReader reader = new StreamReader(mem);
           string text = reader.ReadToEnd();


           LR.MemSrm = text;

           //string memString = text;
           //// convert string to stream
           //byte[] buffer = Encoding.ASCII.GetBytes(memString);
           //MemoryStream ms = new MemoryStream(buffer);
           //write to file
           FileStream file = new FileStream("d:\\file.pdf", FileMode.Create, FileAccess.Write);
           mem.WriteTo(file);
           file.Close();
           mem.Close();


       }