How To Download a File Using ASHX Handler

File downloads can be a bit of a nuance sometimes as web browsers often support a lot of document types. Simply adding the file path to the href of a html element, wont be enough for you to be able to download the file. There are dozens of work arounds to make this work, but using an ASP.NET ashx handler is definitely one of the cleanest methods to do it using code.

I will paste the contents of the entire ashx file below as the script is very simple. This solution will only work if you are using the non razor MVC models that are part of the ASP.NET framework. First you will need to create a new “Generic Handler” this will create a file with a .ashx extension. Once this is done you can point all of your links to this page when you want to download a file. There are many ways you can direct the downloads to this page. To keep things very simple, I have setup the script to accept the file path in the URL of the request.

In order to make the request work you will need to urlencode the value that is being passed into the url. The following code will be all you need to setup the url.

<% filename = "//somepath/folder/myfile.text"; %>
<a href="scripts/Downloadfile.ashx?file=<%= HttpUtility.UrlEncode(filename) %>">Download</a>

You could alternatively use javascript or pretty much anything that is capable of generating a request to your download script. This method has massive security risks, so please take this into consideration. This code will be enough to get a working prototype for you to built upon. This should never be used in any public facing code without some security measures being implemented to stop people tampering with the URL.

namespace scripts
{
    public class Downloadfile : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            HttpContext.Current.Response.ContentType = "application/octet-stream";
            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlDecode(context.Request["file"]));

        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}