How to get the content/type of a file at runtime

Question

I am trying to determine dynamically the content/type of a input file. If I would be in a windows application I could write code like this ( from this blog )

private string GetContentType(string fileName) {
    string contentType = "application/octetstream";
    string ext = System.IO.Path.GetExtension(fileName).ToLower();
    Microsoft.Win32.RegistryKey registryKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(ext);
    if (registryKey != null && registryKey.GetValue("Content Type") != null)
        contentType = registryKey.GetValue("Content Type").ToString();
    return contentType;
} 

What other methods are more suitable for an MVC application?

I would like to use the param within the Controller.File(...) method that receive a filepath and a contentype.

Answer 1

In .Net 4.5 you can use MimeMapping.GetMimeMapping :

string contentType = MimeMapping.GetMimeMapping("someFileName.pdf")
// contentType = "application/pdf"

More information

Answer 2

Important note: This answer was written in 2011, a few years before masterwok's answer was written. Whilst my answer is still acceptable , masterwok's answer is better and more concise. Use and upvote that answer instead. Everything below is for posterity.

I would just use the file extension rather than try to do something clever that may eventually come back to bite you in the arse. :)

The file extension doesn't need to be registered on your system (although I don't know exactly what you're doing with the file...). You could use something like an enum or db table which contains information on acceptable extensions if you want to filter out files.

Please see @Tolgahan's idea on this. I created a C# enum below based on this which should provide people with a starting point should they wish to create a db/enum/xml-based approach to this.

Public enum MimeTypes
{
  [Description("application/postscript")]
  ai,
  [Description("audio/x-aiff")]
  aif,
  [Description("audio/x-aiff")]
  aifc,
  [Description("audio/x-aiff")]
  aiff,
  [Description("text/plain")]
  asc,
  [Description("application/atom+xml")]
  atom,
  [Description("audio/basic")]
  au,
  [Description("video/x-msvideo")]
  avi,
  [Description("application/x-bcpio")]
  bcpio,
  [Description("application/octet-stream")]
  bin,
  [Description("image/bmp")]
  bmp,
  [Description("application/x-netcdf")]
  cdf,
  [Description("image/cgm")]
  cgm,
  [Description("application/octet-stream")]
  class,
  [Description("application/x-cpio")]
  cpio,
  [Description("application/mac-compactpro")]
  cpt,
  [Description("application/x-csh")]
  csh,
  [Description("text/css")]
  css,
  [Description("application/x-director")]
  dcr,
  [Description("video/x-dv")]
  dif,
  [Description("application/x-director")]
  dir,
  [Description("image/vnd.djvu")]
  djv,
  [Description("image/vnd.djvu")]
  djvu,
  [Description("application/octet-stream")]
  dll,
  [Description("application/octet-stream")]
  dmg,
  [Description("application/octet-stream")]
  dms,
  [Description("application/msword")]
  doc,
  [Description("application/xml-dtd")]
  dtd,
  [Description("video/x-dv")]
  dv,
  [Description("application/x-dvi")]
  dvi,
  [Description("application/x-director")]
  dxr,
  [Description("application/postscript")]
  eps,
  [Description("text/x-setext")]
  etx,
  [Description("application/octet-stream")]
  exe,
  [Description("application/andrew-inset")]
  ez,
  [Description("image/gif")]
  gif,
  [Description("application/srgs")]
  gram,
  [Description("application/srgs+xml")]
  grxml,
  [Description("application/x-gtar")]
  gtar,
  [Description("application/x-hdf")]
  hdf,
  [Description("application/mac-binhex40")]
  hqx,
  [Description("text/html")]
  htm,
  [Description("text/html")]
  html,
  [Description("x-conference/x-cooltalk")]
  ice,
  [Description("image/x-icon")]
  ico,
  [Description("text/calendar")]
  ics,
  [Description("image/ief")]
  ief,
  [Description("text/calendar")]
  ifb,
  [Description("model/iges")]
  iges,
  [Description("model/iges")]
  igs,
  [Description("application/x-java-jnlp-file")]
  jnlp,
  [Description("image/jp2")]
  jp2,
  [Description("image/jpeg")]
  jpe,
  [Description("image/jpeg")]
  jpeg,
  [Description("image/jpeg")]
  jpg,
  [Description("application/x-javascript")]
  js,
  [Description("audio/midi")]
  kar,
  [Description("application/x-latex")]
  latex,
  [Description("application/octet-stream")]
  lha,
  [Description("application/octet-stream")]
  lzh,
  [Description("audio/x-mpegurl")]
  m3u,
  [Description("audio/mp4a-latm")]
  m4a,
  [Description("audio/mp4a-latm")]
  m4b,
  [Description("audio/mp4a-latm")]
  m4p,
  [Description("video/vnd.mpegurl")]
  m4u,
  [Description("video/x-m4v")]
  m4v,
  [Description("image/x-macpaint")]
  mac,
  [Description("application/x-troff-man")]
  man,
  [Description("application/mathml+xml")]
  mathml,
  [Description("application/x-troff-me")]
  me,
  [Description("model/mesh")]
  mesh,
  [Description("audio/midi")]
  mid,
  [Description("audio/midi")]
  midi,
  [Description("application/vnd.mif")]
  mif,
  [Description("video/quicktime")]
  mov,
  [Description("video/x-sgi-movie")]
  movie,
  [Description("audio/mpeg")]
  mp2,
  [Description("audio/mpeg")]
  mp3,
  [Description("video/mp4")]
  mp4,
  [Description("video/mpeg")]
  mpe,
  [Description("video/mpeg")]
  mpeg,
  [Description("video/mpeg")]
  mpg,
  [Description("audio/mpeg")]
  mpga,
  [Description("application/x-troff-ms")]
  ms,
  [Description("model/mesh")]
  msh,
  [Description("video/vnd.mpegurl")]
  mxu,
  [Description("application/x-netcdf")]
  nc,
  [Description("application/oda")]
  oda,
  [Description("application/ogg")]
  ogg,
  [Description("image/x-portable-bitmap")]
  pbm,
  [Description("image/pict")]
  pct,
  [Description("chemical/x-pdb")]
  pdb,
  [Description("application/pdf")]
  pdf,
  [Description("image/x-portable-graymap")]
  pgm,
  [Description("application/x-chess-pgn")]
  pgn,
  [Description("image/pict")]
  pic,
  [Description("image/pict")]
  pict,
  [Description("image/png")]
  png,
  [Description("image/x-portable-anymap")]
  pnm,
  [Description("image/x-macpaint")]
  pnt,
  [Description("image/x-macpaint")]
  pntg,
  [Description("image/x-portable-pixmap")]
  ppm,
  [Description("application/vnd.ms-powerpoint")]
  ppt,
  [Description("application/postscript")]
  ps,
  [Description("video/quicktime")]
  qt,
  [Description("image/x-quicktime")]
  qti,
  [Description("image/x-quicktime")]
  qtif,
  [Description("audio/x-pn-realaudio")]
  ra,
  [Description("audio/x-pn-realaudio")]
  ram,
  [Description("image/x-cmu-raster")]
  ras,
  [Description("application/rdf+xml")]
  rdf,
  [Description("image/x-rgb")]
  rgb,
  [Description("application/vnd.rn-realmedia")]
  rm,
  [Description("application/x-troff")]
  roff,
  [Description("text/rtf")]
  rtf,
  [Description("text/richtext")]
  rtx,
  [Description("text/sgml")]
  sgm,
  [Description("text/sgml")]
  sgml,
  [Description("application/x-sh")]
  sh,
  [Description("application/x-shar")]
  shar,
  [Description("model/mesh")]
  silo,
  [Description("application/x-stuffit")]
  sit,
  [Description("application/x-koan")]
  skd,
  [Description("application/x-koan")]
  skm,
  [Description("application/x-koan")]
  skp,
  [Description("application/x-koan")]
  skt,
  [Description("application/smil")]
  smi,
  [Description("application/smil")]
  smil,
  [Description("audio/basic")]
  snd,
  [Description("application/octet-stream")]
  so,
  [Description("application/x-futuresplash")]
  spl,
  [Description("application/x-wais-source")]
  src,
  [Description("application/x-sv4cpio")]
  sv4cpio,
  [Description("application/x-sv4crc")]
  sv4crc,
  [Description("image/svg+xml")]
  svg,
  [Description("application/x-shockwave-flash")]
  swf,
  [Description("application/x-troff")]
  t,
  [Description("application/x-tar")]
  tar,
  [Description("application/x-tcl")]
  tcl,
  [Description("application/x-tex")]
  tex,
  [Description("application/x-texinfo")]
  texi,
  [Description("application/x-texinfo")]
  texinfo,
  [Description("image/tiff")]
  tif,
  [Description("image/tiff")]
  tiff,
  [Description("application/x-troff")]
  tr,
  [Description("text/tab-separated-values")]
  tsv,
  [Description("text/plain")]
  txt,
  [Description("application/x-ustar")]
  ustar,
  [Description("application/x-cdlink")]
  vcd,
  [Description("model/vrml")]
  vrml,
  [Description("application/voicexml+xml")]
  vxml,
  [Description("audio/x-wav")]
  wav,
  [Description("image/vnd.wap.wbmp")]
  wbmp,
  [Description("application/vnd.wap.wbxml")]
  wbmxl,
  [Description("text/vnd.wap.wml")]
  wml,
  [Description("application/vnd.wap.wmlc")]
  wmlc,
  [Description("text/vnd.wap.wmlscript")]
  wmls,
  [Description("application/vnd.wap.wmlscriptc")]
  wmlsc,
  [Description("model/vrml")]
  wrl,
  [Description("image/x-xbitmap")]
  xbm,
  [Description("application/xhtml+xml")]
  xht,
  [Description("application/xhtml+xml")]
  xhtml,
  [Description("application/vnd.ms-excel")]
  xls,
  [Description("application/xml")]
  xml,
  [Description("image/x-xpixmap")]
  xpm,
  [Description("application/xml")]
  xsl,
  [Description("application/xslt+xml")]
  xslt,
  [Description("application/vnd.mozilla.xul+xml")]
  xul,
  [Description("image/x-xwindowdump")]
  xwd,
  [Description("chemical/x-xyz")]
  xyz,
  [Description("application/zip")]
  zip
}

Answer 3

IDEA：将格式和扩展数据（ http://www.feedforall.com/mime-types.htm ）放入 xml 或作为字典、数组或其他东西的项目中以供查询，并创建一个程序来确定扩展的 mimetype ..我认为将您的数据保存在 xml 文档中会更容易在编译后进行修改

Answer 4

.NET CORE Using Microsoft.AspNetCore.StaticFiles

var provider = new FileExtensionContentTypeProvider();
string contentType;
if(!provider.TryGetContentType(fileName, out contentType))
{
    contentType = "application/octet-stream";
}

Answer 5

If you want to use stream

    public class urlmonMimeDetect
    {
        [DllImport(@"urlmon.dll", CharSet = CharSet.Auto)]
        private extern static System.UInt32 FindMimeFromData(
            System.UInt32 pBC,
            [MarshalAs(UnmanagedType.LPStr)] System.String pwzUrl,
            [MarshalAs(UnmanagedType.LPArray)] byte[] pBuffer,
            System.UInt32 cbSize,
            [MarshalAs(UnmanagedType.LPStr)] System.String pwzMimeProposed,
            System.UInt32 dwMimeFlags,
            out System.UInt32 ppwzMimeOut,
            System.UInt32 dwReserverd
        );

        public static string GetMimeFromFile(Stream fs)
        {

            byte[] buffer = new byte[256];
            fs.Read(buffer, 0, 256);

            try
            {
                System.UInt32 mimetype;
                FindMimeFromData(0, null, buffer, 256, null, 0, out mimetype, 0);
                System.IntPtr mimeTypePtr = new IntPtr(mimetype);
                string mime = Marshal.PtrToStringUni(mimeTypePtr);
                Marshal.FreeCoTaskMem(mimeTypePtr);
                return mime;
            }
            catch (Exception e)
            {
                return "unknown/unknown";
            }
        }
    }

Answer 6

Is the file being uploaded to the MVC application?

public ActionResult FileUploader(HttpPostedFileBase upload)
{
  string mimeType=upload.ContentType;
}

There are a couple of caveats with this though.

It uses the browser supplied aka 'client supplied' mime type, if the users uploading items aren't authenticated or trusted, then this might not be a good idea.

Also IE doesn't always give standard Mime types for certain files, in particular PNGs (see What is the difference between "image/png" and "image/x-png"? ) which may or may not effect your application.

We just use a simple if statement to convert the IE png mime type (image/x-png), back to the more common one (image/png).

Answer 7

If you are on a linux/unix like system you can use the file command to determine the file type.

There are three sets of tests, performed in this order: filesystem tests, magic number tests, and language tests. The first test that succeeds causes the file type to be printed.

If you're on a Windows machine it is common to use the file extension like you showed in your code.