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Download file over HTTP from VBA (WinHTTP)

I am trying to (HTTP) download a binary programmatically from VBA. I intend to host an ASPX page on a server to accept a file and some additional options.

I know there are many good ways to do this (like using a webservice instead of aspx), but my limitation is that it has to run in VBA (in an excel file) and that I cannot install any additional components per client.

So, I think I'll be using WinHTTP and I've found some examples for posting form data, but not posting a binary. I probably need to base64 the content of the file?

So my questions are:

  • Do I need to do the encoding manually or can I get WinHTTP to do it?
  • Is there a better utility than WinHTTP? (Remember, I don't want to install any additional software, it must be shipped using WinXP Pro, Office 2007, or the .NET framework, for example.)
  • Is there a better way to go for example. using ASP.NET Web Services?

thanks chiccodoro

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You can use base64, but it's usually easier to write binaries.

The hurdle you have to jump around is creating a valid multipart POST message. This is perfectly possible with WinHTTP, although I haven't done it for years and I haven't been able to provide a sample code, it's not trivial.

You can refer to the following articles for examples of how to do this using C # HttpWebRequest. The WinHTTP api is slightly different, of course, but the main point to take away from the articles is the structure of the POST body.



I usually provide sample code, but as I said, I don't have the Stone Age tools installed right now; -).

NTN

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