Monday, December 10, 2012

Setting a "Content-Disposition" HTTP Header in Web API Controller Method

When developing an ASP.NET Web API controller method that allows to download a file it is considered a good practice to set a "Content-Disposition" header to guide a browser of a name of a file being downloaded.

There are two different ways to approach this simple task. First is to add a new HTTP header to the HTTP response using string values for the header's name and value. The second is to try and use the .NET framework's infrastructure methods that presumably should make this task easier.

The first method seems to be very simple but potentially dangerous: one would need to hard-code string values and be totally responsible for the values to be properly formatted according to the W3C standards.

var response = new HttpResponseMessage();
response.Headers.Add("Content-Disposition", "attachment; filename=fileName.ext");
The second method is to try and delegate handling of the specifics of the HTTP protocol to the .NET framework by using corresponding presumably built-in methods. This seems more appropriate and even easier to achieve. However due to poor documentation of the Web API extensions that is easier said than done. without further ado this is how it's done:

var response = new HttpResponseMessage();
response.Content.Headers.ContentDisposition = 
   new ContentDispositionHeaderValue("attachment") { FileName = fileName};
Only one string value here should hard-coded with a guideline available in the official documentation so it's not that bad.

If you find this information possible share it with your fellow colleagues so it may save their valuable time.