Binary Files

this code works fine to display images, but when I change the strFileName to a .PDF document it doesn't work...is there something else I need to do to view a .PDF?

Code:

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Const strFileName As String = "C:\Inetpub\wwwroot\pbss\interstate.gif"
        Dim objStream As Stream = File.Open(strFileName, FileMode.Open)
        Dim buffer(objStream.Length) As Byte
        objStream.Read(buffer, 0, objStream.Length)
        objStream.Close()
        Response.BinaryWrite(buffer)

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How can I get the .PDF to open in Adobe. The way I have it now it's opening in the browser...

ok, I got it to open in Adobe, but now I'm getting an error in Adobe. I think I'm getting the wrong file size from my app. I'm using: FileByteArray = objDR("bid_document")...but am sure it's returning an inaccurate file size. Does anyone know the way to get the proper file size?