Opening downloaded file from IE in C#

We have created an application that registers a custom file extension, and we have client's asking to download it from a web server. We register the extension on the web server with a MIME type开发者_JAVA技巧 (octet), and it serves it correctly. IE9 and Chrome both launch the application successfully; IE8 seems to lock the file if the user chooses "Open" from the "Save/Open" dialog. Is there a way to get IE to release this lock (or whatever)?

Are the downloaded files encrypted (are you using https)?

If so, look at IE8's Internet Options --> Advanced --> Security --> "Do not save encrypted pages to disk". Disable this option.

We've run into this problem while downloading PDF files over a secure connection. IE8 wasn't opening Adobe Reader since the file hasn't been saved on the disk.

Hope this helps.

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