File MIME type / Content Type

I have a webpage that has FileUpload control to upload files to server. The FileUpload.ContentType is also saved in database and later used in other procedures.

Now I need an equivalent functionality in my webservice. I get the files from user in byte array. But how should I determine the content type? I was stuck on this because there is no native .NET way to get an equivalent of the FileContent of the asp.net FileUpload control.

I tried using the urlmon.dll. But the results for FileUpload.ContentType and the urlmon.dll were different. The FindMimeFromData of urlmon.dll and FileUpload.ContentType return different values for same file.

e.g. For a .csv file, FindMimeFromData returns "text/plain" while the FileUpload ContentType returns "application/vnd.ms-excel".

A detailed discussion about this can be found here: http://www.vbforums.com/showthread.php?t=634382

Finally I decided to build my own class that gets the job done.

The Problem

To build a class that returns the equivalent of asp.net FileUpload control’s ContentType property.

Solution

You can build your own class from the algorithm given here:
http://msdn.microsoft.com/en-us/library/ms775147.aspx

Here’s the class that gives you the equivalent of FileUpload.ContentType property. The MIME types list was picked up from Mendhak’s post in this thread: http://forums.asp.net/t/1143353.aspx. Since the thread is very old, you might need to update the list from other sources that may have a more updated list.

Option Strict On
Imports System.Runtime.InteropServices
Imports System.IO 

Public Class MimeTypes
    Private Shared knownTypes As List(Of String)
    Private Shared mimeTypes As Dictionary(Of String, String)

    <DllImport("urlmon.dll", CharSet:=CharSet.Auto)> _
    Private Shared Function FindMimeFromData(ByVal pBC As UInt32, <MarshalAs(UnmanagedType.LPStr)> ByVal pwzUrl As String, <MarshalAs(UnmanagedType.LPArray)> ByVal pBuffer As Byte(), ByVal cbSize As UInt32, <MarshalAs(UnmanagedType.LPStr)> ByVal pwzMimeProposed As String, ByVal dwMimeFlags As UInt32, ByRef ppwzMimeOut As UInt32, ByVal dwReserverd As UInt32) As UInt32
    End Function

    Public Shared Function GetContentType(ByVal fileName As String) As String
        If knownTypes Is Nothing OrElse mimeTypes Is Nothing Then InitializeMimeTypeLists()
        Dim contentType As String = ""
        Dim extension As String = IO.Path.GetExtension(fileName).Replace(".", "").ToLower
        mimeTypes.TryGetValue(extension, contentType)
        If String.IsNullOrEmpty(contentType) OrElse knownTypes.Contains(contentType) Then
            Dim headerType As String = ScanFileForMimeType(fileName)
            If headerType <> "application/octet-stream" OrElse String.IsNullOrEmpty(contentType) Then contentType = headerType
        End If
        Return contentType
    End Function

    Private Shared Function ScanFileForMimeType(ByVal fileName As String) As String
        Dim buffer As Byte() = New Byte(255) {}
        Using fs As New FileStream(fileName, FileMode.Open)
            Dim readLength As Integer = CInt(Math.Min(256, fs.Length))
            fs.Read(buffer, 0, readLength)
        End Using
        Try
            Dim mimeType As UInt32
            FindMimeFromData(0, Nothing, buffer, 256, Nothing, 0, mimeType, 0)
            Dim mimeTypePtr As IntPtr = New IntPtr(mimeType)
            Dim mime As String = Marshal.PtrToStringUni(mimeTypePtr)
            Marshal.FreeCoTaskMem(mimeTypePtr)
            If String.IsNullOrEmpty(mime) Then mime = "application/octet-stream"
            Return mime
        Catch e As Exception
            Return "application/octet-stream"
        End Try
    End Function

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

References

1. http://forums.asp.net/t/1143353.aspx
2. http://msdn.microsoft.com/en-us/library/ms775147.aspx