MVC HttpResponseMessage for returning content as a file. #attachment, #mvc.

FileDownloadHttpResponseMessage.cs

public class FileDownloadHttpResponseMessage : HttpResponseMessage
{
    public FileDownloadHttpResponseMessage(string fileName, string content)
        : base(HttpStatusCode.OK)
    {
        Content = new StringContent(content);

        // A text file is actually an octet-stream (pdf, etc)
        Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");

        // We used attachment to force download
        Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
        Content.Headers.ContentDisposition.FileName = fileName;
    }
}