greetings and salutations, o smarter than i.
i've been working on a solution to secure the delivery of pdfs to client
browsers. we're introducing an public-website element, so i've decided to use
a webservice on the internal application webserver to pass a pdf as a byte
array to a public webserver outside the LAN, where it can be forwarded on the
response to the client browser.

i could use some advice how to improve this: i'm not entirely satisfied with
the memory useage--i'm trying to shy away from taking on making a ISAPI
extention if i can get this efficient enough as is.

more vexingly, every so often, a local user will experience an error where
the PDF is never saved/opened after they make their choice on the file
open/save dialog. further, msie's progress meter remains and looks like it's
very slowly filling (or timing out) even after the pdf has successfully been
saved/opened--is there a final signal i'm failing to send to the browser..?

I designed the web service as follows:

Public Class DocumentRequest
   Inherits System.Web.Services.WebService

   Private EXAMPLE_DIR As String =
Server.mappath("/ExportedPDFs/ExampleSheets/")

   Private Function BinaryGetPDFDocument(ByVal FileDIR As String, ByVal
FileNum As String) As Byte()
       Dim FileStreamIn As New System.IO.FileStream(FileDIR + FileNum +
".pdf", System.IO.FileMode.Open, System.IO.FileAccess.Read,
System.IO.FileShare.Read)
       Dim PDFData(FileStreamIn.Length) As Byte
       Dim i As Integer = FileStreamIn.Read(PDFData, 0,
CInt(FileStreamIn.Length))
       While (i < CInt(FileStreamIn.Length))
           System.Threading.Thread.Sleep(200)
       End While
       FileStreamIn.Close()
       Return PDFData
   End Function

   Private Function CheckExistsPDFDocument(ByVal FileDIR As String, ByVal
FileNum As String) As Boolean
       Try
           If (System.IO.File.Exists(FileDIR + FileNum + ".pdf")) Then
               Return True
           Else
               Return False
           End If
       Catch
           Return False
       End Try
   End Function

   <WebMethod()> _
   Public Function GetExampleSheet(ByVal FileNum As String) As Byte()
       Return BinaryGetPDFDocument(EXAMPLE_DIR, FileNum)
   End Function

   <WebMethod()> _
   Public Function CheckExistsExampleSheet(ByVal FileNum As String) As
Boolean
       Return CheckExistsPDFDocument(EXAMPLE_DIR, FileNum)
   End Function

End Class

and i wrote a consume function as follows:

   Friend Sub PushPDFtoClient(ByRef Response As System.Web.HttpResponse,
ByVal FileNum As String, ByVal TYPE As String)
       Dim ws As New PDFRequest.DocumentRequest
       Dim PDFData() As Byte

       Try
           If (TYPE = "EXAMPLE") Then
               PDFData = ws.GetExampleSheet(FileNum)
           End If
       Catch ex As Exception
          'EDITED - removed some private logging functions
           Response.Write("<script language=""javascript""
type=""text/javascript"">alert('There was an unexpected error accessing the
PDF')</script>")
           Exit Sub
       End Try

       Dim ms As System.IO.MemoryStream = New System.IO.MemoryStream(PDFData)
       Response.Clear()
       Response.ContentType = "application/octet-stream"
       Response.AddHeader("Content-Disposition", "attachment; filename=" &
TYPE & "-" & FileNum & ".pdf; size=" & PDFData.Length.ToString)
       Response.AddHeader("Content-Length", PDFData.Length.ToString)
       Response.Flush()

       Dim chunkSize As Integer = 1024
       Dim i As Integer
       For i = 0 To PDFData.Length Step chunkSize

           If (Not Response.IsClientConnected) Then
               Exit For
           End If

           Dim size As Integer = chunkSize
           If (i + chunkSize >= PDFData.Length) Then
               size = (PDFData.Length - i)
           End

           Dim chunk(size - 1) As Byte
           ms.Read(chunk, 0, size)
           Response.BinaryWrite(chunk)
           Response.Flush()
       Next
       ms.Close()
       Response.End()
   End Sub