Determine the file type using C#

I have a web page that has the file upload component to upload the allowed document types only to my system (images only). I don't want to use the regular expression to determine the file type and using the extension.

Please let me know if there is any other means of determining file types in C#.

Answers


I've just converted my VB.NET class to C# to detect mime types. They will be identified by a mix of sniffing the first 256 Bytes of a file(urlmon.dll - f.e. used by internet explorer) and a set of known types.

You can also use it to check if the file is what it pretends to be(if the extension matches the type).

// check whether or not the uploaded file is an image:
var contentType = MimeTypes.GetContentType(FileUpload1.PostedFile.FileName);
if(contentType.StartsWith("image"))
{
    // do something with the image ...
}

Here's the class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.IO;

public class MimeTypes
{
    private static List<string> knownTypes;

    private static Dictionary<string, string> mimeTypes;

    [DllImport("urlmon.dll", CharSet = CharSet.Auto)]
    private static extern UInt32 FindMimeFromData(
        UInt32 pBC, [MarshalAs(UnmanagedType.LPStr)]
        string pwzUrl, [MarshalAs(UnmanagedType.LPArray)]
        byte[] pBuffer, UInt32 cbSize, [MarshalAs(UnmanagedType.LPStr)]
        string pwzMimeProposed, UInt32 dwMimeFlags, ref UInt32 ppwzMimeOut, UInt32 dwReserverd
    );

    public static string GetContentType(string fileName)
    {
        if (knownTypes == null || mimeTypes == null)
            InitializeMimeTypeLists();
        string contentType = "";
        string extension = System.IO.Path.GetExtension(fileName).Replace(".", "").ToLower();
        mimeTypes.TryGetValue(extension, out contentType);
        if (string.IsNullOrEmpty(contentType) || knownTypes.Contains(contentType))
        {
            string headerType = ScanFileForMimeType(fileName);
            if (headerType != "application/octet-stream" || string.IsNullOrEmpty(contentType))
                contentType = headerType;
        }
        return contentType;
    }

    private static string ScanFileForMimeType(string fileName)
    {
        try
        {
            byte[] buffer = new byte[256];
            using (FileStream fs = new FileStream(fileName, FileMode.Open))
            {
                int readLength = Convert.ToInt32(Math.Min(256, fs.Length));
                fs.Read(buffer, 0, readLength);
            }

            UInt32 mimeType = default(UInt32);
            FindMimeFromData(0, null, buffer, 256, null, 0, ref mimeType, 0);
            IntPtr mimeTypePtr = new IntPtr(mimeType);
            string mime = Marshal.PtrToStringUni(mimeTypePtr);
            Marshal.FreeCoTaskMem(mimeTypePtr);
            if (string.IsNullOrEmpty(mime))
                mime = "application/octet-stream";
            return mime;
        } catch (Exception ex)
        {
            return "application/octet-stream";
        }
    }

    private static void InitializeMimeTypeLists()
    {
        knownTypes = new string[] {
        "text/plain",
        "text/html",
        "text/xml",
        "text/richtext",
        "text/scriptlet",
        "audio/x-aiff",
        "audio/basic",
        "audio/mid",
        "audio/wav",
        "image/gif",
        "image/jpeg",
        "image/pjpeg",
        "image/png",
        "image/x-png",
        "image/tiff",
        "image/bmp",
        "image/x-xbitmap",
        "image/x-jg",
        "image/x-emf",
        "image/x-wmf",
        "video/avi",
        "video/mpeg",
        "application/octet-stream",
        "application/postscript",
        "application/base64",
        "application/macbinhex40",
        "application/pdf",
        "application/xml",
        "application/atom+xml",
        "application/rss+xml",
        "application/x-compressed",
        "application/x-zip-compressed",
        "application/x-gzip-compressed",
        "application/java",
        "application/x-msdownload"
    }.ToList();

        mimeTypes = new Dictionary<string, string>();
        mimeTypes.Add("3dm", "x-world/x-3dmf");
        mimeTypes.Add("3dmf", "x-world/x-3dmf");
        mimeTypes.Add("a", "application/octet-stream");
        mimeTypes.Add("aab", "application/x-authorware-bin");
        mimeTypes.Add("aam", "application/x-authorware-map");
        mimeTypes.Add("aas", "application/x-authorware-seg");
        mimeTypes.Add("abc", "text/vnd.abc");
        mimeTypes.Add("acgi", "text/html");
        mimeTypes.Add("afl", "video/animaflex");
        mimeTypes.Add("ai", "application/postscript");
        mimeTypes.Add("aif", "audio/aiff");
        mimeTypes.Add("aifc", "audio/aiff");
        mimeTypes.Add("aiff", "audio/aiff");
        mimeTypes.Add("aim", "application/x-aim");
        mimeTypes.Add("aip", "text/x-audiosoft-intra");
        mimeTypes.Add("ani", "application/x-navi-animation");
        mimeTypes.Add("aos", "application/x-nokia-9000-communicator-add-on-software");
        mimeTypes.Add("aps", "application/mime");
        mimeTypes.Add("arc", "application/octet-stream");
        mimeTypes.Add("arj", "application/arj");
        mimeTypes.Add("art", "image/x-jg");
        mimeTypes.Add("asf", "video/x-ms-asf");
        mimeTypes.Add("asm", "text/x-asm");
        mimeTypes.Add("asp", "text/asp");
        mimeTypes.Add("asx", "application/x-mplayer2");
        mimeTypes.Add("au", "audio/basic");
        mimeTypes.Add("avi", "video/avi");
        mimeTypes.Add("avs", "video/avs-video");
        mimeTypes.Add("bcpio", "application/x-bcpio");
        mimeTypes.Add("bin", "application/octet-stream");
        mimeTypes.Add("bm", "image/bmp");
        mimeTypes.Add("bmp", "image/bmp");
        mimeTypes.Add("boo", "application/book");
        mimeTypes.Add("book", "application/book");
        mimeTypes.Add("boz", "application/x-bzip2");
        mimeTypes.Add("bsh", "application/x-bsh");
        mimeTypes.Add("bz", "application/x-bzip");
        mimeTypes.Add("bz2", "application/x-bzip2");
        mimeTypes.Add("c", "text/plain");
        mimeTypes.Add("c++", "text/plain");
        mimeTypes.Add("cat", "application/vnd.ms-pki.seccat");
        mimeTypes.Add("cc", "text/plain");
        mimeTypes.Add("ccad", "application/clariscad");
        mimeTypes.Add("cco", "application/x-cocoa");
        mimeTypes.Add("cdf", "application/cdf");
        mimeTypes.Add("cer", "application/pkix-cert");
        mimeTypes.Add("cha", "application/x-chat");
        mimeTypes.Add("chat", "application/x-chat");
        mimeTypes.Add("class", "application/java");
        mimeTypes.Add("com", "application/octet-stream");
        mimeTypes.Add("conf", "text/plain");
        mimeTypes.Add("cpio", "application/x-cpio");
        mimeTypes.Add("cpp", "text/x-c");
        mimeTypes.Add("cpt", "application/x-cpt");
        mimeTypes.Add("crl", "application/pkcs-crl");
        mimeTypes.Add("css", "text/css");
        mimeTypes.Add("def", "text/plain");
        mimeTypes.Add("der", "application/x-x509-ca-cert");
        mimeTypes.Add("dif", "video/x-dv");
        mimeTypes.Add("dir", "application/x-director");
        mimeTypes.Add("dl", "video/dl");
        mimeTypes.Add("doc", "application/msword");
        mimeTypes.Add("dot", "application/msword");
        mimeTypes.Add("dp", "application/commonground");
        mimeTypes.Add("drw", "application/drafting");
        mimeTypes.Add("dump", "application/octet-stream");
        mimeTypes.Add("dv", "video/x-dv");
        mimeTypes.Add("dvi", "application/x-dvi");
        mimeTypes.Add("dwf", "drawing/x-dwf (old)");
        mimeTypes.Add("dwg", "application/acad");
        mimeTypes.Add("dxf", "application/dxf");
        mimeTypes.Add("eps", "application/postscript");
        mimeTypes.Add("es", "application/x-esrehber");
        mimeTypes.Add("etx", "text/x-setext");
        mimeTypes.Add("evy", "application/envoy");
        mimeTypes.Add("exe", "application/octet-stream");
        mimeTypes.Add("f", "text/plain");
        mimeTypes.Add("f90", "text/x-fortran");
        mimeTypes.Add("fdf", "application/vnd.fdf");
        mimeTypes.Add("fif", "image/fif");
        mimeTypes.Add("fli", "video/fli");
        mimeTypes.Add("flv", "video/x-flv");
        mimeTypes.Add("for", "text/x-fortran");
        mimeTypes.Add("fpx", "image/vnd.fpx");
        mimeTypes.Add("g", "text/plain");
        mimeTypes.Add("g3", "image/g3fax");
        mimeTypes.Add("gif", "image/gif");
        mimeTypes.Add("gl", "video/gl");
        mimeTypes.Add("gsd", "audio/x-gsm");
        mimeTypes.Add("gtar", "application/x-gtar");
        mimeTypes.Add("gz", "application/x-compressed");
        mimeTypes.Add("h", "text/plain");
        mimeTypes.Add("help", "application/x-helpfile");
        mimeTypes.Add("hgl", "application/vnd.hp-hpgl");
        mimeTypes.Add("hh", "text/plain");
        mimeTypes.Add("hlp", "application/x-winhelp");
        mimeTypes.Add("htc", "text/x-component");
        mimeTypes.Add("htm", "text/html");
        mimeTypes.Add("html", "text/html");
        mimeTypes.Add("htmls", "text/html");
        mimeTypes.Add("htt", "text/webviewhtml");
        mimeTypes.Add("htx", "text/html");
        mimeTypes.Add("ice", "x-conference/x-cooltalk");
        mimeTypes.Add("ico", "image/x-icon");
        mimeTypes.Add("idc", "text/plain");
        mimeTypes.Add("ief", "image/ief");
        mimeTypes.Add("iefs", "image/ief");
        mimeTypes.Add("iges", "application/iges");
        mimeTypes.Add("igs", "application/iges");
        mimeTypes.Add("ima", "application/x-ima");
        mimeTypes.Add("imap", "application/x-httpd-imap");
        mimeTypes.Add("inf", "application/inf");
        mimeTypes.Add("ins", "application/x-internett-signup");
        mimeTypes.Add("ip", "application/x-ip2");
        mimeTypes.Add("isu", "video/x-isvideo");
        mimeTypes.Add("it", "audio/it");
        mimeTypes.Add("iv", "application/x-inventor");
        mimeTypes.Add("ivr", "i-world/i-vrml");
        mimeTypes.Add("ivy", "application/x-livescreen");
        mimeTypes.Add("jam", "audio/x-jam");
        mimeTypes.Add("jav", "text/plain");
        mimeTypes.Add("java", "text/plain");
        mimeTypes.Add("jcm", "application/x-java-commerce");
        mimeTypes.Add("jfif", "image/jpeg");
        mimeTypes.Add("jfif-tbnl", "image/jpeg");
        mimeTypes.Add("jpe", "image/jpeg");
        mimeTypes.Add("jpeg", "image/jpeg");
        mimeTypes.Add("jpg", "image/jpeg");
        mimeTypes.Add("jps", "image/x-jps");
        mimeTypes.Add("js", "application/x-javascript");
        mimeTypes.Add("jut", "image/jutvision");
        mimeTypes.Add("kar", "audio/midi");
        mimeTypes.Add("ksh", "application/x-ksh");
        mimeTypes.Add("la", "audio/nspaudio");
        mimeTypes.Add("lam", "audio/x-liveaudio");
        mimeTypes.Add("latex", "application/x-latex");
        mimeTypes.Add("lha", "application/lha");
        mimeTypes.Add("lhx", "application/octet-stream");
        mimeTypes.Add("list", "text/plain");
        mimeTypes.Add("lma", "audio/nspaudio");
        mimeTypes.Add("log", "text/plain");
        mimeTypes.Add("lsp", "application/x-lisp");
        mimeTypes.Add("lst", "text/plain");
        mimeTypes.Add("lsx", "text/x-la-asf");
        mimeTypes.Add("ltx", "application/x-latex");
        mimeTypes.Add("lzh", "application/octet-stream");
        mimeTypes.Add("lzx", "application/lzx");
        mimeTypes.Add("m", "text/plain");
        mimeTypes.Add("m1v", "video/mpeg");
        mimeTypes.Add("m2a", "audio/mpeg");
        mimeTypes.Add("m2v", "video/mpeg");
        mimeTypes.Add("m3u", "audio/x-mpequrl");
        mimeTypes.Add("man", "application/x-troff-man");
        mimeTypes.Add("map", "application/x-navimap");
        mimeTypes.Add("mar", "text/plain");
        mimeTypes.Add("mbd", "application/mbedlet");
        mimeTypes.Add("mc$", "application/x-magic-cap-package-1.0");
        mimeTypes.Add("mcd", "application/mcad");
        mimeTypes.Add("mcf", "image/vasa");
        mimeTypes.Add("mcp", "application/netmc");
        mimeTypes.Add("me", "application/x-troff-me");
        mimeTypes.Add("mht", "message/rfc822");
        mimeTypes.Add("mhtml", "message/rfc822");
        mimeTypes.Add("mid", "audio/midi");
        mimeTypes.Add("midi", "audio/midi");
        mimeTypes.Add("mif", "application/x-frame");
        mimeTypes.Add("mime", "message/rfc822");
        mimeTypes.Add("mjf", "audio/x-vnd.audioexplosion.mjuicemediafile");
        mimeTypes.Add("mjpg", "video/x-motion-jpeg");
        mimeTypes.Add("mm", "application/base64");
        mimeTypes.Add("mme", "application/base64");
        mimeTypes.Add("mod", "audio/mod");
        mimeTypes.Add("moov", "video/quicktime");
        mimeTypes.Add("mov", "video/quicktime");
        mimeTypes.Add("movie", "video/x-sgi-movie");
        mimeTypes.Add("mp2", "audio/mpeg");
        mimeTypes.Add("mp3", "audio/mpeg3");
        mimeTypes.Add("mpa", "audio/mpeg");
        mimeTypes.Add("mpc", "application/x-project");
        mimeTypes.Add("mpe", "video/mpeg");
        mimeTypes.Add("mpeg", "video/mpeg");
        mimeTypes.Add("mpg", "video/mpeg");
        mimeTypes.Add("mpga", "audio/mpeg");
        mimeTypes.Add("mpp", "application/vnd.ms-project");
        mimeTypes.Add("mpt", "application/x-project");
        mimeTypes.Add("mpv", "application/x-project");
        mimeTypes.Add("mpx", "application/x-project");
        mimeTypes.Add("mrc", "application/marc");
        mimeTypes.Add("ms", "application/x-troff-ms");
        mimeTypes.Add("mv", "video/x-sgi-movie");
        mimeTypes.Add("my", "audio/make");
        mimeTypes.Add("mzz", "application/x-vnd.audioexplosion.mzz");
        mimeTypes.Add("nap", "image/naplps");
        mimeTypes.Add("naplps", "image/naplps");
        mimeTypes.Add("nc", "application/x-netcdf");
        mimeTypes.Add("ncm", "application/vnd.nokia.configuration-message");
        mimeTypes.Add("nif", "image/x-niff");
        mimeTypes.Add("niff", "image/x-niff");
        mimeTypes.Add("nix", "application/x-mix-transfer");
        mimeTypes.Add("nsc", "application/x-conference");
        mimeTypes.Add("nvd", "application/x-navidoc");
        mimeTypes.Add("o", "application/octet-stream");
        mimeTypes.Add("oda", "application/oda");
        mimeTypes.Add("omc", "application/x-omc");
        mimeTypes.Add("omcd", "application/x-omcdatamaker");
        mimeTypes.Add("omcr", "application/x-omcregerator");
        mimeTypes.Add("p", "text/x-pascal");
        mimeTypes.Add("p10", "application/pkcs10");
        mimeTypes.Add("p12", "application/pkcs-12");
        mimeTypes.Add("p7a", "application/x-pkcs7-signature");
        mimeTypes.Add("p7c", "application/pkcs7-mime");
        mimeTypes.Add("pas", "text/pascal");
        mimeTypes.Add("pbm", "image/x-portable-bitmap");
        mimeTypes.Add("pcl", "application/vnd.hp-pcl");
        mimeTypes.Add("pct", "image/x-pict");
        mimeTypes.Add("pcx", "image/x-pcx");
        mimeTypes.Add("pdf", "application/pdf");
        mimeTypes.Add("pfunk", "audio/make");
        mimeTypes.Add("pgm", "image/x-portable-graymap");
        mimeTypes.Add("pic", "image/pict");
        mimeTypes.Add("pict", "image/pict");
        mimeTypes.Add("pkg", "application/x-newton-compatible-pkg");
        mimeTypes.Add("pko", "application/vnd.ms-pki.pko");
        mimeTypes.Add("pl", "text/plain");
        mimeTypes.Add("plx", "application/x-pixclscript");
        mimeTypes.Add("pm", "image/x-xpixmap");
        mimeTypes.Add("png", "image/png");
        mimeTypes.Add("pnm", "application/x-portable-anymap");
        mimeTypes.Add("pot", "application/mspowerpoint");
        mimeTypes.Add("pov", "model/x-pov");
        mimeTypes.Add("ppa", "application/vnd.ms-powerpoint");
        mimeTypes.Add("ppm", "image/x-portable-pixmap");
        mimeTypes.Add("pps", "application/mspowerpoint");
        mimeTypes.Add("ppt", "application/mspowerpoint");
        mimeTypes.Add("ppz", "application/mspowerpoint");
        mimeTypes.Add("pre", "application/x-freelance");
        mimeTypes.Add("prt", "application/pro_eng");
        mimeTypes.Add("ps", "application/postscript");
        mimeTypes.Add("psd", "application/octet-stream");
        mimeTypes.Add("pvu", "paleovu/x-pv");
        mimeTypes.Add("pwz", "application/vnd.ms-powerpoint");
        mimeTypes.Add("py", "text/x-script.phyton");
        mimeTypes.Add("pyc", "applicaiton/x-bytecode.python");
        mimeTypes.Add("qcp", "audio/vnd.qcelp");
        mimeTypes.Add("qd3", "x-world/x-3dmf");
        mimeTypes.Add("qd3d", "x-world/x-3dmf");
        mimeTypes.Add("qif", "image/x-quicktime");
        mimeTypes.Add("qt", "video/quicktime");
        mimeTypes.Add("qtc", "video/x-qtc");
        mimeTypes.Add("qti", "image/x-quicktime");
        mimeTypes.Add("qtif", "image/x-quicktime");
        mimeTypes.Add("ra", "audio/x-pn-realaudio");
        mimeTypes.Add("ram", "audio/x-pn-realaudio");
        mimeTypes.Add("ras", "application/x-cmu-raster");
        mimeTypes.Add("rast", "image/cmu-raster");
        mimeTypes.Add("rexx", "text/x-script.rexx");
        mimeTypes.Add("rf", "image/vnd.rn-realflash");
        mimeTypes.Add("rgb", "image/x-rgb");
        mimeTypes.Add("rm", "application/vnd.rn-realmedia");
        mimeTypes.Add("rmi", "audio/mid");
        mimeTypes.Add("rmm", "audio/x-pn-realaudio");
        mimeTypes.Add("rmp", "audio/x-pn-realaudio");
        mimeTypes.Add("rng", "application/ringing-tones");
        mimeTypes.Add("rnx", "application/vnd.rn-realplayer");
        mimeTypes.Add("roff", "application/x-troff");
        mimeTypes.Add("rp", "image/vnd.rn-realpix");
        mimeTypes.Add("rpm", "audio/x-pn-realaudio-plugin");
        mimeTypes.Add("rt", "text/richtext");
        mimeTypes.Add("rtf", "text/richtext");
        mimeTypes.Add("rtx", "application/rtf");
        mimeTypes.Add("rv", "video/vnd.rn-realvideo");
        mimeTypes.Add("s", "text/x-asm");
        mimeTypes.Add("s3m", "audio/s3m");
        mimeTypes.Add("saveme", "application/octet-stream");
        mimeTypes.Add("sbk", "application/x-tbook");
        mimeTypes.Add("scm", "application/x-lotusscreencam");
        mimeTypes.Add("sdml", "text/plain");
        mimeTypes.Add("sdp", "application/sdp");
        mimeTypes.Add("sdr", "application/sounder");
        mimeTypes.Add("sea", "application/sea");
        mimeTypes.Add("set", "application/set");
        mimeTypes.Add("sgm", "text/sgml");
        mimeTypes.Add("sgml", "text/sgml");
        mimeTypes.Add("sh", "application/x-bsh");
        mimeTypes.Add("shtml", "text/html");
        mimeTypes.Add("sid", "audio/x-psid");
        mimeTypes.Add("sit", "application/x-sit");
        mimeTypes.Add("skd", "application/x-koan");
        mimeTypes.Add("skm", "application/x-koan");
        mimeTypes.Add("skp", "application/x-koan");
        mimeTypes.Add("skt", "application/x-koan");
        mimeTypes.Add("sl", "application/x-seelogo");
        mimeTypes.Add("smi", "application/smil");
        mimeTypes.Add("smil", "application/smil");
        mimeTypes.Add("snd", "audio/basic");
        mimeTypes.Add("sol", "application/solids");
        mimeTypes.Add("spc", "application/x-pkcs7-certificates");
        mimeTypes.Add("spl", "application/futuresplash");
        mimeTypes.Add("spr", "application/x-sprite");
        mimeTypes.Add("sprite", "application/x-sprite");
        mimeTypes.Add("src", "application/x-wais-source");
        mimeTypes.Add("ssi", "text/x-server-parsed-html");
        mimeTypes.Add("ssm", "application/streamingmedia");
        mimeTypes.Add("sst", "application/vnd.ms-pki.certstore");
        mimeTypes.Add("step", "application/step");
        mimeTypes.Add("stl", "application/sla");
        mimeTypes.Add("stp", "application/step");
        mimeTypes.Add("sv4cpio", "application/x-sv4cpio");
        mimeTypes.Add("sv4crc", "application/x-sv4crc");
        mimeTypes.Add("svf", "image/vnd.dwg");
        mimeTypes.Add("svr", "application/x-world");
        mimeTypes.Add("swf", "application/x-shockwave-flash");
        mimeTypes.Add("t", "application/x-troff");
        mimeTypes.Add("talk", "text/x-speech");
        mimeTypes.Add("tar", "application/x-tar");
        mimeTypes.Add("tbk", "application/toolbook");
        mimeTypes.Add("tcl", "application/x-tcl");
        mimeTypes.Add("tcsh", "text/x-script.tcsh");
        mimeTypes.Add("tex", "application/x-tex");
        mimeTypes.Add("texi", "application/x-texinfo");
        mimeTypes.Add("texinfo", "application/x-texinfo");
        mimeTypes.Add("text", "text/plain");
        mimeTypes.Add("tgz", "application/x-compressed");
        mimeTypes.Add("tif", "image/tiff");
        mimeTypes.Add("tr", "application/x-troff");
        mimeTypes.Add("tsi", "audio/tsp-audio");
        mimeTypes.Add("tsp", "audio/tsplayer");
        mimeTypes.Add("tsv", "text/tab-separated-values");
        mimeTypes.Add("turbot", "image/florian");
        mimeTypes.Add("txt", "text/plain");
        mimeTypes.Add("uil", "text/x-uil");
        mimeTypes.Add("uni", "text/uri-list");
        mimeTypes.Add("unis", "text/uri-list");
        mimeTypes.Add("unv", "application/i-deas");
        mimeTypes.Add("uri", "text/uri-list");
        mimeTypes.Add("uris", "text/uri-list");
        mimeTypes.Add("ustar", "application/x-ustar");
        mimeTypes.Add("uu", "application/octet-stream");
        mimeTypes.Add("vcd", "application/x-cdlink");
        mimeTypes.Add("vcs", "text/x-vcalendar");
        mimeTypes.Add("vda", "application/vda");
        mimeTypes.Add("vdo", "video/vdo");
        mimeTypes.Add("vew", "application/groupwise");
        mimeTypes.Add("viv", "video/vivo");
        mimeTypes.Add("vivo", "video/vivo");
        mimeTypes.Add("vmd", "application/vocaltec-media-desc");
        mimeTypes.Add("vmf", "application/vocaltec-media-file");
        mimeTypes.Add("voc", "audio/voc");
        mimeTypes.Add("vos", "video/vosaic");
        mimeTypes.Add("vox", "audio/voxware");
        mimeTypes.Add("vqe", "audio/x-twinvq-plugin");
        mimeTypes.Add("vqf", "audio/x-twinvq");
        mimeTypes.Add("vql", "audio/x-twinvq-plugin");
        mimeTypes.Add("vrml", "application/x-vrml");
        mimeTypes.Add("vrt", "x-world/x-vrt");
        mimeTypes.Add("vsd", "application/x-visio");
        mimeTypes.Add("vst", "application/x-visio");
        mimeTypes.Add("vsw", "application/x-visio");
        mimeTypes.Add("w60", "application/wordperfect6.0");
        mimeTypes.Add("w61", "application/wordperfect6.1");
        mimeTypes.Add("w6w", "application/msword");
        mimeTypes.Add("wav", "audio/wav");
        mimeTypes.Add("wb1", "application/x-qpro");
        mimeTypes.Add("wbmp", "image/vnd.wap.wbmp");
        mimeTypes.Add("web", "application/vnd.xara");
        mimeTypes.Add("wiz", "application/msword");
        mimeTypes.Add("wk1", "application/x-123");
        mimeTypes.Add("wmf", "windows/metafile");
        mimeTypes.Add("wml", "text/vnd.wap.wml");
        mimeTypes.Add("wmlc", "application/vnd.wap.wmlc");
        mimeTypes.Add("wmls", "text/vnd.wap.wmlscript");
        mimeTypes.Add("wmlsc", "application/vnd.wap.wmlscriptc");
        mimeTypes.Add("word", "application/msword");
        mimeTypes.Add("wp", "application/wordperfect");
        mimeTypes.Add("wp5", "application/wordperfect");
        mimeTypes.Add("wp6", "application/wordperfect");
        mimeTypes.Add("wpd", "application/wordperfect");
        mimeTypes.Add("wq1", "application/x-lotus");
        mimeTypes.Add("wri", "application/mswrite");
        mimeTypes.Add("wrl", "application/x-world");
        mimeTypes.Add("wrz", "model/vrml");
        mimeTypes.Add("wsc", "text/scriplet");
        mimeTypes.Add("wsrc", "application/x-wais-source");
        mimeTypes.Add("wtk", "application/x-wintalk");
        mimeTypes.Add("xbm", "image/x-xbitmap");
        mimeTypes.Add("xdr", "video/x-amt-demorun");
        mimeTypes.Add("xgz", "xgl/drawing");
        mimeTypes.Add("xif", "image/vnd.xiff");
        mimeTypes.Add("xl", "application/excel");
        mimeTypes.Add("xla", "application/excel");
        mimeTypes.Add("xlb", "application/excel");
        mimeTypes.Add("xlc", "application/excel");
        mimeTypes.Add("xld", "application/excel");
        mimeTypes.Add("xlk", "application/excel");
        mimeTypes.Add("xll", "application/excel");
        mimeTypes.Add("xlm", "application/excel");
        mimeTypes.Add("xls", "application/excel");
        mimeTypes.Add("xlsx", "application/excel");
        mimeTypes.Add("xlt", "application/excel");
        mimeTypes.Add("xlv", "application/excel");
        mimeTypes.Add("xlw", "application/excel");
        mimeTypes.Add("xm", "audio/xm");
        mimeTypes.Add("xml", "text/xml");
        mimeTypes.Add("xmz", "xgl/movie");
        mimeTypes.Add("xpix", "application/x-vnd.ls-xpix");
        mimeTypes.Add("xpm", "image/x-xpixmap");
        mimeTypes.Add("x-png", "image/png");
        mimeTypes.Add("xsr", "video/x-amt-showrun");
        mimeTypes.Add("xwd", "image/x-xwd");
        mimeTypes.Add("xyz", "chemical/x-pdb");
        mimeTypes.Add("z", "application/x-compress");
        mimeTypes.Add("zip", "application/x-compressed");
        mimeTypes.Add("zoo", "application/octet-stream");
        mimeTypes.Add("zsh", "text/x-script.zsh");
    }
}

You have to update this list when a mime type is unknown and it is not sufficient to know that it is application/octet-stream. It might suffice to check if an extension is txt but the mime-type is binary data, because that means that this file is not what it pretends to be.


Apart from that it's really easier to use a RegularExpressionValidator.

For example (only jpg-images):

<asp:FileUpload ID="FileUpload1" runat="server" /><br />
<br />
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" 
 Text="Upload File" />&nbsp;<br />
<br />
<asp:Label ID="Label1" runat="server"></asp:Label>
<asp:RegularExpressionValidator 
 id="RegularExpressionValidator1" runat="server" 
 ErrorMessage="Only jpeg files are allowed!" 
 ValidationExpression="^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))
    +(.jpg|.JPG|.jpeg|.JPEG)$" 
 ControlToValidate="FileUpload1"></asp:RegularExpressionValidator>

In codebehind:

if (FileUpload1.HasFile)
{
    string fileExt = 
       System.IO.Path.GetExtension(FileUpload1.FileName);

    if (fileExt == ".jpeg" || fileExt == ".jpg")
    {
        //do what you want with this image
    }
    else
    {
        Label1.Text = "Only .jpeg files are allowed!";
    }
}

There is a helper class in .NET for that, called Path. What you need is

Path.GetExtension();

It is located in the System.IO namespace.


you can use Myrmec to identify the file type, this library use the file byte head. this library avaliable on nuget "Myrmec",and this is the repo, myrmec also support mime type,you can try it. the code will like this :

// create a sniffer instance.
Sniffer sniffer = new Sniffer();

// populate with mata data.
sniffer.Populate(FileTypes.CommonFileTypes);

// get file head byte, may be 20 bytes enough.
byte[] fileHead = ReadFileHead();

// start match.
List<string> results = sniffer.Match(fileHead);

        HttpFileCollection hfc = Request.Files;
        for (int i = 0; i < hfc.Count - 1; i++)
        {
            HttpPostedFile hpf = hfc(i);
            if (hpf.ContentType == "image/jpeg")
            {

                //its a jpeg

            }
        }

Saw an example that was along the lines of this. Should point you in the right direction. From msdn site.

string fileName = @"C:\mydir.old\myfile.ext";
string path = @"C:\mydir.old\";
string extension;

extension = Path.GetExtension(fileName);
Console.WriteLine("GetExtension('{0}') returns '{1}'", 
fileName, extension);

extension = Path.GetExtension(path);
Console.WriteLine("GetExtension('{0}') returns '{1}'", 
path, extension);

// This code produces output similar to the following:
//
// GetExtension('C:\mydir.old\myfile.ext') returns '.ext'
// GetExtension('C:\mydir.old\') returns ''

It sounds like you're looking for FindMimeFromData. There's a lot of additional info and code in this question.


Need Your Help

"ERROR: Cannot recover key" When Exporting Signed Android App with Existing Keystore

android export apk keystore android-keystore

I have an existing keystore with a password and a few keys with different passwords inside for the different apps I have exported and uploaded to Google Play.