How To Read and Display Binary Data in ASP


This article shows how to read and display binary data using Active Server Pages.

Many developers appreciate the ease of using the Scripting.FileSystemObject to open an ASCII file and then display its contents in Microsoft Word or Microsoft Excel from within Internet Explorer. In its current inception, ASP does not directly provide any comparable objects to read files that contain binary data such as an Excel worksheet with macros, an Adobe Acrobat (.pdf) file, a .gif image, or any other files that contain binary data. However, an ASP developer can write a custom business object or component that adds this functionality.

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Part I provides the ASP code that receives and then displays the binary file using an appropriate MIME type, and Part II shows how to create the Visual Basic 5.0 (or later) ActiveX DLL component that extends the capability of ASP to read binary data.

Part I: ASP Sample That Opens an Excel Worksheet Containing Macros

Response.buffer = TRUE
Response.ContentType = "application/x-msexcel"

Dim vntStream

Set oMyObject = Server.CreateObject("MyObject.BinRead")
vntStream = oMyObject.readBinFile("c:\temp\tempxls.xls")


Set oMyObject = Nothing


NOTE: For Acrobat files, change the MIME type by using Response.ContentType = "application/pdf". For a .gif image, use Response.ContentType = "image/gif".

Part II: The Visual Basic 5.0 ActiveX DLL (MyObject.BinRead)

To create the component that performs the binary read, perform the following steps:

  1. Create a new ActiveX DLL project in Visual Basic 5.0 or later.
  2. Rename the project MyObject.
  3. Rename the class module BinRead.
  4. Cut and paste the following code into the General Declarations section of the class module:

       Function readBinFile(ByVal bfilename As String) As Variant
    Dim fl As Long
    Dim FileNum As Long
    Dim binbyte() As Byte
    Dim binfilestr As String

    On Error GoTo errHandler

    FileNum = FreeFile
    Open bfilename For Binary Access Read As #FileNum

    fl = FileLen(bfilename)
    ReDim binbyte(fl)

    Get #FileNum, , binbyte

    Close #FileNum

    readBinFile = binbyte
    Exit Function

    Exit Function
    End Function
  5. Save the project.
  6. On the File menu click Make MyObject.dll.
If your Web server is on a separate machine from where you created the component, you need to copy the component onto the Web server and register it using RegSvr32.

To incorporate the file created in Part I into another ASP page that has text or other formatting, use a server side include statement.