Question

I need the browser to open file types it understands directly in the browser (i.e. no “Open/Save/Cancel” dialog.

Here’s my code, which currently works great!…except that every file pops up the dialog box and doesn’t directly open the file:

string filePath = Path.Combine(WebConfigurationManager.AppSettings["NewsAttachmentPath"], context.Request.QueryString["FileName"]);
byte[] bytes = System.IO.File.ReadAllBytes(filePath);
context.Response.Clear();
context.Response.ContentType = "application/octet-stream";
context.Response.Cache.SetCacheability(HttpCacheability.Private);
context.Response.Expires = -1;
context.Response.Buffer = true;
context.Response.AddHeader("Content-Disposition", string.Format("{0};FileName=\"{1}\"", "inline", context.Request.QueryString["FileName"]));
context.Response.BinaryWrite(bytes);
context.Response.End();

As you can see, even when I change the Content-Disposition to “inline”, it still prompts for download. This is with files that I know my browser understands. In other words, I can go to some random site and click a PDF, and it will open in the browser. My site will make me save it in order to view it.

Pre-emptive answer to “why do you wanna use application/octet-stream?” Because I don’t want to create a handler for each single file type. If this is mistaken, please let me know.

Answer 1

You do not need to create a handler per file type. You just change the line:

context.Response.ContentType = "application/octet-stream";

to be:

string contentType = //your logic here, possibly many lines in a separate method
context.Response.ContentType = contentType;

But no: you can’t “inline” an application/octet-stream. That means “here’s some bytes, but I don’t know what they are”. The browser can’t do much with that, other than save it somewhere, hence a download prompt. You can use content-disposition to suggest a filename, though.

The browser does not work on file extensions – it works on content-type. So: you need to report the correct content-type in your response. This might mean writing a switch / lookup based on the file extension that you know, or it might mean storing the explicit content-type separately as metadata along with the file information.