we wrote CMS apps with asp.net. the user can attach file documents, pdfs to their forms and send to each other. the user can easily download the pdf and other documents but when they want to download jpg file their IE render the jpg file as a binary and show the binaries of jpg file? the IE didn't show the save as dialogue such as other files!
where is problem? and how can I handle this in asp.net? Is it relate to HTTPS? because the user used the https to connect to this cms.
As I understand it, users need to download the files and they are able to do so for some files but not for JPEG? And it shows as binary, what do you mean, it shows the byte codes?
Keep in mind each request has a content type header in the response which will identify to the browser what kind of content it is. This is set a known MIME type such as image/jpeg, ...
Content-Type: text/html; charset=utf-8
Browser loads each resource based on the content type. Having said that, it is up to the browser to load the resource the way it wants. I can personalise and change my browser setting to some point so you have to look at the user's browser if you cannot reproduce it on each machine.
In any case, you need to see the content-type header in the response for the resource (using Fiddler as someone else also suggested) and make sure it is set to a correct value. If it is set to image/jpeg, it will render it as image but if it is set to application/octet-stream it will download it. My hunch is it is set to something else (such as text/html or text/plain) and that is why browser tries to show it as a text.