What are the differences between
Response.AddHeader("content-disposition", "attachment;filename=somefile.ext")
and
Response.AddHeader("content-disposition", "inline;filename=somefile.ext")
I don't know the differences , because when I use one or another I always get a window prompt asking me to download the file for both of them. I read the specs, but it is clueless.
If it is inline, the browser should attempt to render it within the browser window. If it cannot, it will resort to an external program, prompting the user.
With attachment, it will immediately go to the user, and not try to load it in the browser, whether it can or not.
Because when I use one or another I get a window prompt asking me to download the file for both of them.
This behavior depends on the browser and the file you are trying to serve. With inline, the browser will try to open the file within the browser.
For example, if you have a PDF file and Firefox/Adobe Reader, an inline disposition will open the PDF within Firefox, whereas attachment will force it to download.
If you're serving a .ZIP file, browsers won't be able to display it inline, so for inline and attachment dispositions, the file will be downloaded.