Download file of any type in Asp.Net MVC using FileResult?

Question

I've had it suggested to me that I should use FileResult to allow users to download files from my Asp.Net MVC application. But the only examples of this I can find always has to do with image files (specifying content type image/jpeg).

But what if I can't know the file type? I want users to be able to download pretty much any file from the filearea of my site.

I had read one method of doing this (see a previous post for the code), that actually works fine, except for one thing: the name of the file that comes up in the Save As dialog is concatenated from the file path with underscores (folder_folder_file.ext). Also, it seems people think I should return a FileResult instead of using this custom class that I had found BinaryContentResult.

Anyone know the "correct" way of doing such a download in MVC?

EDIT: I got the answer (below), but just thought I should post the full working code if someone else is interested:

    public ActionResult Download(string filePath, string fileName)
    {
        string fullName = Path.Combine(GetBaseDir(), filePath, fileName);

        byte[] fileBytes = GetFile(fullName);
        return File(fileBytes, System.Net.Mime.MediaTypeNames.Application.Octet, fileName);
    }

    byte[] GetFile(string s)
    {

        System.IO.FileStream fs = System.IO.File.OpenRead(s);
        byte[] data = new byte[fs.Length];
        int br = fs.Read(data, 0, data.Length);
        if (br != fs.Length)
            throw new System.IO.IOException(s);
        return data;
    }

Answer 1

Phil Haack has a nice article where he created a Custome File Download Action Result class. You only need to specify the virtual path of the file and the name to be saved as.

I used it once and here's my code.

        [AcceptVerbs(HttpVerbs.Get)]
        public ActionResult Download(int fileID)
        {
            Data.LinqToSql.File file = _fileService.GetByID(fileID);

            return new DownloadResult { VirtualPath = GetVirtualPath(file.Path),
                                        FileDownloadName = file.Name };
        }

In my example i was storing the physical path of the files so i used this helper method -that i found somewhere i can't remember- to convert it to a virtual path

        private string GetVirtualPath(string physicalPath)
        {
            string rootpath = Server.MapPath("~/");

            physicalPath = physicalPath.Replace(rootpath, "");
            physicalPath = physicalPath.Replace("\\", "/");

            return "~/" + physicalPath;
        }

Here's the full class as taken from Phill Haack's article

public class DownloadResult : ActionResult {

    public DownloadResult() {}

    public DownloadResult(string virtualPath) {
        this.VirtualPath = virtualPath;
    }

    public string VirtualPath {
        get;
        set;
    }

    public string FileDownloadName {
        get;
        set;
    }

    public override void ExecuteResult(ControllerContext context) {
        if (!String.IsNullOrEmpty(FileDownloadName)) {
            context.HttpContext.Response.AddHeader("content-disposition", 
            "attachment; filename=" + this.FileDownloadName)
        }

        string filePath = context.HttpContext.Server.MapPath(this.VirtualPath);
        context.HttpContext.Response.TransmitFile(filePath);
    }
}

Answer 2

You can just specify the generic octet-stream MIME type:

public FileResult Download()
{
    byte[] fileBytes = ...;
    string fileName = "example";
    return File(fileBytes, System.Net.Mime.MediaTypeNames.Application.Octet, fileName);
}