Today I had to generate files in ASP.NET for download which was supposed to open a save file dialog in the web brower. The file name was based on a title field extracted from a database. The title had spaces which I allowed to be used in the file name (I replaced accents and other invalid characters). In the source code bellow you can see a simple illustrative example.
Perhaps you have noticed that I am generating a plain text file, but I am not using the “text/plain” mime type. When you use “text/plain” the browser automatically knows which application to use for opening the file. If you use “application/octet-stream” instead, the browser uses the file extension in order to find out which is the operating system default program for that file extension. But when you have spaces in you file name as in the example above, you get different behaviours from different browsers.
In Internet Explorer 7, the spaces are replaced by underscores, the the browser recognizes the file extension “.txt”.
If you download the same generated file using Firefox, it cuts the file name ending at the first space. This way the browser considers that your file name is “Just” which has no extension. As a consequence Firefox doesn’t know which application to suggest you for opening the file.
I haven’t tried other browsers, but I took a safe approach. In the server side, while defining the file name I replace the spaces by underscores, this way the download has a consistent behavior in both browsers.
