MVC2 File Download

I am first getting the file bytes


[COLOR=blue]byte[/COLOR][] fileBytes = [COLOR=#2b91af]File[/COLOR].ReadAllBytes(destinationFilePath);

And then push the file out


return File(fileBytes, [COLOR=#2b91af]FileContentType[/COLOR].ApplicationOctetStream, fileName);

For small files this is great but for big files like 20mb and above, the conversion takes time.

How can i make it better so that conversion time gets better?

Is there some third party component available that can do the job better?