Indice dei contenuti
Come posso recuperare il MIME Type di un determinato file in C#? Si tratta di una domanda molto frequente tra sviluppatori e che mi capita di sentire spesso da amici e colleghi che lavorano sul framework ASP.NET per realizzare applicazioni MVC, Web API e (ultimamente) .NET Core. Il motivo è semplice: se si lavora di frequente con filesystem e database prima o poi arriva sempre la necessità di recuperare il MIME type di un file, ad esempio al momento di inviarlo al browser dell'utente al termine di una request. In tutti i casi in cui il MIME Type non è stato memorizzato in precedenza, non possiamo fare altro che recuperarlo basandoci sull'estensione del file in questione, che nella maggior parte dei casi fornisce un indizio inequivocabile per identificare la tipologia di file da inviare: abbiamo quindi bisogno di effettuare un mapping tra le varie possibili estensioni che possono avere i nostri file e il MIME Type corrispondente a ciascuna di esse.
Esistono numerose tecniche che consentono di svolgere questa operazione in modo più o meno efficiente. Per ragioni di semplicità ci limiteremo ad approfondirne due: recuperare le informazioni contenute dal Registro di sistema (Windows Registry) o utilizzare a tale scopo una lista statica di tipi MIME (MIME Type Map). Non prenderemo in considerazione tecniche che prevedono di effettuare delle interrogazioni a servizi esterni, in quanto riteniamo che un simile approccio sarebbe assolutamente inefficiente per questo tipo di necessità.
Recupero dal Registro di Sistema
Questa tecnica si basa sull'assunto, tanto ovvio quanto veritierio, che le informazioni relative ai tipi MIME più utilizzati siano già presenti in un archivio apposito nel nostro sistema operativo, per la precisione - nel caso dei sistemi Windows - in una apposita chiave di registro: tutto quello che dobbiamo fare è trovare il modo corretto per interrogarlo. Il vantaggio principale di questo approccio è dato dalla sua intrinseca semplicità: per effettuare questa interrogazione bastano poche linee di codice.
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/// <summary> /// Retrieves the MimeType bound to the given filename or extension by looking into the Windows Registry entries. /// NOTE: This method supports only the MimeTypes registered in the server OS / Windows installation. /// </summary> /// <param name="fileNameOrExtension">a valid filename (file.txt) or extension (.txt or txt)</param> /// <returns>A valid Mime Type (es. text/plain)</returns> public static string GetMimeTypeByWindowsRegistry(string fileNameOrExtension) { string mimeType = "application/unknown"; string ext = (fileNameOrExtension.Contains(".")) ? System.IO.Path.GetExtension(fileNameOrExtension).ToLower() : "." + fileNameOrExtension; Microsoft.Win32.RegistryKey regKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(ext); if (regKey != null && regKey.GetValue("Content Type") != null) mimeType = regKey.GetValue("Content Type").ToString(); return mimeType; } |
Il problema principale di questa tecnica è dato dalla necessità che i MIME-Type che ci interessa supportare siano effettivamente registrati nel Sistema Operativo dove l'applicazione è installata. Tutte le volte in cui questo assunto non è vero, la nostra interrogazione non restituirà alcun risultato e non saremo quindi in grado di recuperare il MIME Type corretto. Contrariamente a quello che si può pensare, non si tratta di un problema da poco: il sistema operativo possiede una collezione di MIME Type piuttosto minimale, quasi sempre limitata ai tipi di file che può aprire con una delle applicazioni installate. Il problema è particolarmente evidente se stiamo lavorando con una applicazione web, poiché i Server Web dispongono solitamente di un numero limitato di applicativi installati: lo stretto indispensabile per poter funzionare, così da tenere le risorse di sistema libere per IIS o altri servizi necessari.
Recupero da una MIME Type Map
Per risolvere le limitazioni del metodo precedente è possibile dotarsi (o realizzare manualmente) una classe apposita contenente un elenco dei tipi MIME corrispondenti a tutte le estensioni file più diffuse. Tra le molte disponibili in rete, la più completa - per C# - è senza dubbio quella fornita a corredo di questo progetto GitHub. Questa classe, oltre a contenere un numero enorme di MIME Type, prevede un mapping deterministico a due vie che consente anche di fare l'opposto, ovvero recuperare l'estensione corrispondente a un determinato tipo MIME.
Di seguito il codice completo della classe, aggiornato al 31 gennaio 2017:
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using System; using System.Collections.Generic; using System.Linq; namespace MimeTypes { public static class MimeTypeMap { private static readonly Lazy<IDictionary<string, string>> _mappings = new Lazy<IDictionary<string, string>>(BuildMappings); private static IDictionary<string, string> BuildMappings() { var mappings = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase) { #region Big freaking list of mime types // maps both ways, // extension -> mime type // and // mime type -> extension // // any mime types on left side not pre-loaded on right side, are added automatically // some mime types can map to multiple extensions, so to get a deterministic mapping, // add those to the dictionary specifcially // // combination of values from Windows 7 Registry and // from C:\Windows\System32\inetsrv\config\applicationHost.config // some added, including .7z and .dat // // Some added based on http://www.iana.org/assignments/media-types/media-types.xhtml // which lists mime types, but not extensions // {".323", "text/h323"}, {".3g2", "video/3gpp2"}, {".3gp", "video/3gpp"}, {".3gp2", "video/3gpp2"}, {".3gpp", "video/3gpp"}, {".7z", "application/x-7z-compressed"}, {".aa", "audio/audible"}, {".AAC", "audio/aac"}, {".aaf", "application/octet-stream"}, {".aax", "audio/vnd.audible.aax"}, {".ac3", "audio/ac3"}, {".aca", "application/octet-stream"}, {".accda", "application/msaccess.addin"}, {".accdb", "application/msaccess"}, {".accdc", "application/msaccess.cab"}, {".accde", "application/msaccess"}, {".accdr", "application/msaccess.runtime"}, {".accdt", "application/msaccess"}, {".accdw", "application/msaccess.webapplication"}, {".accft", "application/msaccess.ftemplate"}, {".acx", "application/internet-property-stream"}, {".AddIn", "text/xml"}, {".ade", "application/msaccess"}, {".adobebridge", "application/x-bridge-url"}, {".adp", "application/msaccess"}, {".ADT", "audio/vnd.dlna.adts"}, {".ADTS", "audio/aac"}, {".afm", "application/octet-stream"}, {".ai", "application/postscript"}, {".aif", "audio/aiff"}, {".aifc", "audio/aiff"}, {".aiff", "audio/aiff"}, {".air", "application/vnd.adobe.air-application-installer-package+zip"}, {".amc", "application/mpeg"}, {".anx", "application/annodex"}, {".apk", "application/vnd.android.package-archive" }, {".application", "application/x-ms-application"}, {".art", "image/x-jg"}, {".asa", "application/xml"}, {".asax", "application/xml"}, {".ascx", "application/xml"}, {".asd", "application/octet-stream"}, {".asf", "video/x-ms-asf"}, {".ashx", "application/xml"}, {".asi", "application/octet-stream"}, {".asm", "text/plain"}, {".asmx", "application/xml"}, {".aspx", "application/xml"}, {".asr", "video/x-ms-asf"}, {".asx", "video/x-ms-asf"}, {".atom", "application/atom+xml"}, {".au", "audio/basic"}, {".avi", "video/x-msvideo"}, {".axa", "audio/annodex"}, {".axs", "application/olescript"}, {".axv", "video/annodex"}, {".bas", "text/plain"}, {".bcpio", "application/x-bcpio"}, {".bin", "application/octet-stream"}, {".bmp", "image/bmp"}, {".c", "text/plain"}, {".cab", "application/octet-stream"}, {".caf", "audio/x-caf"}, {".calx", "application/vnd.ms-office.calx"}, {".cat", "application/vnd.ms-pki.seccat"}, {".cc", "text/plain"}, {".cd", "text/plain"}, {".cdda", "audio/aiff"}, {".cdf", "application/x-cdf"}, {".cer", "application/x-x509-ca-cert"}, {".cfg", "text/plain"}, {".chm", "application/octet-stream"}, {".class", "application/x-java-applet"}, {".clp", "application/x-msclip"}, {".cmd", "text/plain"}, {".cmx", "image/x-cmx"}, {".cnf", "text/plain"}, {".cod", "image/cis-cod"}, {".config", "application/xml"}, {".contact", "text/x-ms-contact"}, {".coverage", "application/xml"}, {".cpio", "application/x-cpio"}, {".cpp", "text/plain"}, {".crd", "application/x-mscardfile"}, {".crl", "application/pkix-crl"}, {".crt", "application/x-x509-ca-cert"}, {".cs", "text/plain"}, {".csdproj", "text/plain"}, {".csh", "application/x-csh"}, {".csproj", "text/plain"}, {".css", "text/css"}, {".csv", "text/csv"}, {".cur", "application/octet-stream"}, {".cxx", "text/plain"}, {".dat", "application/octet-stream"}, {".datasource", "application/xml"}, {".dbproj", "text/plain"}, {".dcr", "application/x-director"}, {".def", "text/plain"}, {".deploy", "application/octet-stream"}, {".der", "application/x-x509-ca-cert"}, {".dgml", "application/xml"}, {".dib", "image/bmp"}, {".dif", "video/x-dv"}, {".dir", "application/x-director"}, {".disco", "text/xml"}, {".divx", "video/divx"}, {".dll", "application/x-msdownload"}, {".dll.config", "text/xml"}, {".dlm", "text/dlm"}, {".doc", "application/msword"}, {".docm", "application/vnd.ms-word.document.macroEnabled.12"}, {".docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document"}, {".dot", "application/msword"}, {".dotm", "application/vnd.ms-word.template.macroEnabled.12"}, {".dotx", "application/vnd.openxmlformats-officedocument.wordprocessingml.template"}, {".dsp", "application/octet-stream"}, {".dsw", "text/plain"}, {".dtd", "text/xml"}, {".dtsConfig", "text/xml"}, {".dv", "video/x-dv"}, {".dvi", "application/x-dvi"}, {".dwf", "drawing/x-dwf"}, {".dwp", "application/octet-stream"}, {".dxr", "application/x-director"}, {".eml", "message/rfc822"}, {".emz", "application/octet-stream"}, {".eot", "application/vnd.ms-fontobject"}, {".eps", "application/postscript"}, {".etl", "application/etl"}, {".etx", "text/x-setext"}, {".evy", "application/envoy"}, {".exe", "application/octet-stream"}, {".exe.config", "text/xml"}, {".fdf", "application/vnd.fdf"}, {".fif", "application/fractals"}, {".filters", "application/xml"}, {".fla", "application/octet-stream"}, {".flac", "audio/flac"}, {".flr", "x-world/x-vrml"}, {".flv", "video/x-flv"}, {".fsscript", "application/fsharp-script"}, {".fsx", "application/fsharp-script"}, {".generictest", "application/xml"}, {".gif", "image/gif"}, {".gpx", "application/gpx+xml"}, {".group", "text/x-ms-group"}, {".gsm", "audio/x-gsm"}, {".gtar", "application/x-gtar"}, {".gz", "application/x-gzip"}, {".h", "text/plain"}, {".hdf", "application/x-hdf"}, {".hdml", "text/x-hdml"}, {".hhc", "application/x-oleobject"}, {".hhk", "application/octet-stream"}, {".hhp", "application/octet-stream"}, {".hlp", "application/winhlp"}, {".hpp", "text/plain"}, {".hqx", "application/mac-binhex40"}, {".hta", "application/hta"}, {".htc", "text/x-component"}, {".htm", "text/html"}, {".html", "text/html"}, {".htt", "text/webviewhtml"}, {".hxa", "application/xml"}, {".hxc", "application/xml"}, {".hxd", "application/octet-stream"}, {".hxe", "application/xml"}, {".hxf", "application/xml"}, {".hxh", "application/octet-stream"}, {".hxi", "application/octet-stream"}, {".hxk", "application/xml"}, {".hxq", "application/octet-stream"}, {".hxr", "application/octet-stream"}, {".hxs", "application/octet-stream"}, {".hxt", "text/html"}, {".hxv", "application/xml"}, {".hxw", "application/octet-stream"}, {".hxx", "text/plain"}, {".i", "text/plain"}, {".ico", "image/x-icon"}, {".ics", "application/octet-stream"}, {".idl", "text/plain"}, {".ief", "image/ief"}, {".iii", "application/x-iphone"}, {".inc", "text/plain"}, {".inf", "application/octet-stream"}, {".ini", "text/plain"}, {".inl", "text/plain"}, {".ins", "application/x-internet-signup"}, {".ipa", "application/x-itunes-ipa"}, {".ipg", "application/x-itunes-ipg"}, {".ipproj", "text/plain"}, {".ipsw", "application/x-itunes-ipsw"}, {".iqy", "text/x-ms-iqy"}, {".isp", "application/x-internet-signup"}, {".ite", "application/x-itunes-ite"}, {".itlp", "application/x-itunes-itlp"}, {".itms", "application/x-itunes-itms"}, {".itpc", "application/x-itunes-itpc"}, {".IVF", "video/x-ivf"}, {".jar", "application/java-archive"}, {".java", "application/octet-stream"}, {".jck", "application/liquidmotion"}, {".jcz", "application/liquidmotion"}, {".jfif", "image/pjpeg"}, {".jnlp", "application/x-java-jnlp-file"}, {".jpb", "application/octet-stream"}, {".jpe", "image/jpeg"}, {".jpeg", "image/jpeg"}, {".jpg", "image/jpeg"}, {".js", "application/javascript"}, {".json", "application/json"}, {".jsx", "text/jscript"}, {".jsxbin", "text/plain"}, {".latex", "application/x-latex"}, {".library-ms", "application/windows-library+xml"}, {".lit", "application/x-ms-reader"}, {".loadtest", "application/xml"}, {".lpk", "application/octet-stream"}, {".lsf", "video/x-la-asf"}, {".lst", "text/plain"}, {".lsx", "video/x-la-asf"}, {".lzh", "application/octet-stream"}, {".m13", "application/x-msmediaview"}, {".m14", "application/x-msmediaview"}, {".m1v", "video/mpeg"}, {".m2t", "video/vnd.dlna.mpeg-tts"}, {".m2ts", "video/vnd.dlna.mpeg-tts"}, {".m2v", "video/mpeg"}, {".m3u", "audio/x-mpegurl"}, {".m3u8", "audio/x-mpegurl"}, {".m4a", "audio/m4a"}, {".m4b", "audio/m4b"}, {".m4p", "audio/m4p"}, {".m4r", "audio/x-m4r"}, {".m4v", "video/x-m4v"}, {".mac", "image/x-macpaint"}, {".mak", "text/plain"}, {".man", "application/x-troff-man"}, {".manifest", "application/x-ms-manifest"}, {".map", "text/plain"}, {".master", "application/xml"}, {".mda", "application/msaccess"}, {".mdb", "application/x-msaccess"}, {".mde", "application/msaccess"}, {".mdp", "application/octet-stream"}, {".me", "application/x-troff-me"}, {".mfp", "application/x-shockwave-flash"}, {".mht", "message/rfc822"}, {".mhtml", "message/rfc822"}, {".mid", "audio/mid"}, {".midi", "audio/mid"}, {".mix", "application/octet-stream"}, {".mk", "text/plain"}, {".mmf", "application/x-smaf"}, {".mno", "text/xml"}, {".mny", "application/x-msmoney"}, {".mod", "video/mpeg"}, {".mov", "video/quicktime"}, {".movie", "video/x-sgi-movie"}, {".mp2", "video/mpeg"}, {".mp2v", "video/mpeg"}, {".mp3", "audio/mpeg"}, {".mp4", "video/mp4"}, {".mp4v", "video/mp4"}, {".mpa", "video/mpeg"}, {".mpe", "video/mpeg"}, {".mpeg", "video/mpeg"}, {".mpf", "application/vnd.ms-mediapackage"}, {".mpg", "video/mpeg"}, {".mpp", "application/vnd.ms-project"}, {".mpv2", "video/mpeg"}, {".mqv", "video/quicktime"}, {".ms", "application/x-troff-ms"}, {".msi", "application/octet-stream"}, {".mso", "application/octet-stream"}, {".mts", "video/vnd.dlna.mpeg-tts"}, {".mtx", "application/xml"}, {".mvb", "application/x-msmediaview"}, {".mvc", "application/x-miva-compiled"}, {".mxp", "application/x-mmxp"}, {".nc", "application/x-netcdf"}, {".nsc", "video/x-ms-asf"}, {".nws", "message/rfc822"}, {".ocx", "application/octet-stream"}, {".oda", "application/oda"}, {".odb", "application/vnd.oasis.opendocument.database"}, {".odc", "application/vnd.oasis.opendocument.chart"}, {".odf", "application/vnd.oasis.opendocument.formula"}, {".odg", "application/vnd.oasis.opendocument.graphics"}, {".odh", "text/plain"}, {".odi", "application/vnd.oasis.opendocument.image"}, {".odl", "text/plain"}, {".odm", "application/vnd.oasis.opendocument.text-master"}, {".odp", "application/vnd.oasis.opendocument.presentation"}, {".ods", "application/vnd.oasis.opendocument.spreadsheet"}, {".odt", "application/vnd.oasis.opendocument.text"}, {".oga", "audio/ogg"}, {".ogg", "audio/ogg"}, {".ogv", "video/ogg"}, {".ogx", "application/ogg"}, {".one", "application/onenote"}, {".onea", "application/onenote"}, {".onepkg", "application/onenote"}, {".onetmp", "application/onenote"}, {".onetoc", "application/onenote"}, {".onetoc2", "application/onenote"}, {".opus", "audio/ogg"}, {".orderedtest", "application/xml"}, {".osdx", "application/opensearchdescription+xml"}, {".otf", "application/font-sfnt"}, {".otg", "application/vnd.oasis.opendocument.graphics-template"}, {".oth", "application/vnd.oasis.opendocument.text-web"}, {".otp", "application/vnd.oasis.opendocument.presentation-template"}, {".ots", "application/vnd.oasis.opendocument.spreadsheet-template"}, {".ott", "application/vnd.oasis.opendocument.text-template"}, {".oxt", "application/vnd.openofficeorg.extension"}, {".p10", "application/pkcs10"}, {".p12", "application/x-pkcs12"}, {".p7b", "application/x-pkcs7-certificates"}, {".p7c", "application/pkcs7-mime"}, {".p7m", "application/pkcs7-mime"}, {".p7r", "application/x-pkcs7-certreqresp"}, {".p7s", "application/pkcs7-signature"}, {".pbm", "image/x-portable-bitmap"}, {".pcast", "application/x-podcast"}, {".pct", "image/pict"}, {".pcx", "application/octet-stream"}, {".pcz", "application/octet-stream"}, {".pdf", "application/pdf"}, {".pfb", "application/octet-stream"}, {".pfm", "application/octet-stream"}, {".pfx", "application/x-pkcs12"}, {".pgm", "image/x-portable-graymap"}, {".pic", "image/pict"}, {".pict", "image/pict"}, {".pkgdef", "text/plain"}, {".pkgundef", "text/plain"}, {".pko", "application/vnd.ms-pki.pko"}, {".pls", "audio/scpls"}, {".pma", "application/x-perfmon"}, {".pmc", "application/x-perfmon"}, {".pml", "application/x-perfmon"}, {".pmr", "application/x-perfmon"}, {".pmw", "application/x-perfmon"}, {".png", "image/png"}, {".pnm", "image/x-portable-anymap"}, {".pnt", "image/x-macpaint"}, {".pntg", "image/x-macpaint"}, {".pnz", "image/png"}, {".pot", "application/vnd.ms-powerpoint"}, {".potm", "application/vnd.ms-powerpoint.template.macroEnabled.12"}, {".potx", "application/vnd.openxmlformats-officedocument.presentationml.template"}, {".ppa", "application/vnd.ms-powerpoint"}, {".ppam", "application/vnd.ms-powerpoint.addin.macroEnabled.12"}, {".ppm", "image/x-portable-pixmap"}, {".pps", "application/vnd.ms-powerpoint"}, {".ppsm", "application/vnd.ms-powerpoint.slideshow.macroEnabled.12"}, {".ppsx", "application/vnd.openxmlformats-officedocument.presentationml.slideshow"}, {".ppt", "application/vnd.ms-powerpoint"}, {".pptm", "application/vnd.ms-powerpoint.presentation.macroEnabled.12"}, {".pptx", "application/vnd.openxmlformats-officedocument.presentationml.presentation"}, {".prf", "application/pics-rules"}, {".prm", "application/octet-stream"}, {".prx", "application/octet-stream"}, {".ps", "application/postscript"}, {".psc1", "application/PowerShell"}, {".psd", "application/octet-stream"}, {".psess", "application/xml"}, {".psm", "application/octet-stream"}, {".psp", "application/octet-stream"}, {".pub", "application/x-mspublisher"}, {".pwz", "application/vnd.ms-powerpoint"}, {".qht", "text/x-html-insertion"}, {".qhtm", "text/x-html-insertion"}, {".qt", "video/quicktime"}, {".qti", "image/x-quicktime"}, {".qtif", "image/x-quicktime"}, {".qtl", "application/x-quicktimeplayer"}, {".qxd", "application/octet-stream"}, {".ra", "audio/x-pn-realaudio"}, {".ram", "audio/x-pn-realaudio"}, {".rar", "application/x-rar-compressed"}, {".ras", "image/x-cmu-raster"}, {".rat", "application/rat-file"}, {".rc", "text/plain"}, {".rc2", "text/plain"}, {".rct", "text/plain"}, {".rdlc", "application/xml"}, {".reg", "text/plain"}, {".resx", "application/xml"}, {".rf", "image/vnd.rn-realflash"}, {".rgb", "image/x-rgb"}, {".rgs", "text/plain"}, {".rm", "application/vnd.rn-realmedia"}, {".rmi", "audio/mid"}, {".rmp", "application/vnd.rn-rn_music_package"}, {".roff", "application/x-troff"}, {".rpm", "audio/x-pn-realaudio-plugin"}, {".rqy", "text/x-ms-rqy"}, {".rtf", "application/rtf"}, {".rtx", "text/richtext"}, {".ruleset", "application/xml"}, {".s", "text/plain"}, {".safariextz", "application/x-safari-safariextz"}, {".scd", "application/x-msschedule"}, {".scr", "text/plain"}, {".sct", "text/scriptlet"}, {".sd2", "audio/x-sd2"}, {".sdp", "application/sdp"}, {".sea", "application/octet-stream"}, {".searchConnector-ms", "application/windows-search-connector+xml"}, {".setpay", "application/set-payment-initiation"}, {".setreg", "application/set-registration-initiation"}, {".settings", "application/xml"}, {".sgimb", "application/x-sgimb"}, {".sgml", "text/sgml"}, {".sh", "application/x-sh"}, {".shar", "application/x-shar"}, {".shtml", "text/html"}, {".sit", "application/x-stuffit"}, {".sitemap", "application/xml"}, {".skin", "application/xml"}, {".sldm", "application/vnd.ms-powerpoint.slide.macroEnabled.12"}, {".sldx", "application/vnd.openxmlformats-officedocument.presentationml.slide"}, {".slk", "application/vnd.ms-excel"}, {".sln", "text/plain"}, {".slupkg-ms", "application/x-ms-license"}, {".smd", "audio/x-smd"}, {".smi", "application/octet-stream"}, {".smx", "audio/x-smd"}, {".smz", "audio/x-smd"}, {".snd", "audio/basic"}, {".snippet", "application/xml"}, {".snp", "application/octet-stream"}, {".sol", "text/plain"}, {".sor", "text/plain"}, {".spc", "application/x-pkcs7-certificates"}, {".spl", "application/futuresplash"}, {".spx", "audio/ogg"}, {".src", "application/x-wais-source"}, {".srf", "text/plain"}, {".SSISDeploymentManifest", "text/xml"}, {".ssm", "application/streamingmedia"}, {".sst", "application/vnd.ms-pki.certstore"}, {".stl", "application/vnd.ms-pki.stl"}, {".sv4cpio", "application/x-sv4cpio"}, {".sv4crc", "application/x-sv4crc"}, {".svc", "application/xml"}, {".svg", "image/svg+xml"}, {".swf", "application/x-shockwave-flash"}, {".step", "application/step"}, {".stp", "application/step"}, {".t", "application/x-troff"}, {".tar", "application/x-tar"}, {".tcl", "application/x-tcl"}, {".testrunconfig", "application/xml"}, {".testsettings", "application/xml"}, {".tex", "application/x-tex"}, {".texi", "application/x-texinfo"}, {".texinfo", "application/x-texinfo"}, {".tgz", "application/x-compressed"}, {".thmx", "application/vnd.ms-officetheme"}, {".thn", "application/octet-stream"}, {".tif", "image/tiff"}, {".tiff", "image/tiff"}, {".tlh", "text/plain"}, {".tli", "text/plain"}, {".toc", "application/octet-stream"}, {".tr", "application/x-troff"}, {".trm", "application/x-msterminal"}, {".trx", "application/xml"}, {".ts", "video/vnd.dlna.mpeg-tts"}, {".tsv", "text/tab-separated-values"}, {".ttf", "application/font-sfnt"}, {".tts", "video/vnd.dlna.mpeg-tts"}, {".txt", "text/plain"}, {".u32", "application/octet-stream"}, {".uls", "text/iuls"}, {".user", "text/plain"}, {".ustar", "application/x-ustar"}, {".vb", "text/plain"}, {".vbdproj", "text/plain"}, {".vbk", "video/mpeg"}, {".vbproj", "text/plain"}, {".vbs", "text/vbscript"}, {".vcf", "text/x-vcard"}, {".vcproj", "application/xml"}, {".vcs", "text/plain"}, {".vcxproj", "application/xml"}, {".vddproj", "text/plain"}, {".vdp", "text/plain"}, {".vdproj", "text/plain"}, {".vdx", "application/vnd.ms-visio.viewer"}, {".vml", "text/xml"}, {".vscontent", "application/xml"}, {".vsct", "text/xml"}, {".vsd", "application/vnd.visio"}, {".vsi", "application/ms-vsi"}, {".vsix", "application/vsix"}, {".vsixlangpack", "text/xml"}, {".vsixmanifest", "text/xml"}, {".vsmdi", "application/xml"}, {".vspscc", "text/plain"}, {".vss", "application/vnd.visio"}, {".vsscc", "text/plain"}, {".vssettings", "text/xml"}, {".vssscc", "text/plain"}, {".vst", "application/vnd.visio"}, {".vstemplate", "text/xml"}, {".vsto", "application/x-ms-vsto"}, {".vsw", "application/vnd.visio"}, {".vsx", "application/vnd.visio"}, {".vtx", "application/vnd.visio"}, {".wav", "audio/wav"}, {".wave", "audio/wav"}, {".wax", "audio/x-ms-wax"}, {".wbk", "application/msword"}, {".wbmp", "image/vnd.wap.wbmp"}, {".wcm", "application/vnd.ms-works"}, {".wdb", "application/vnd.ms-works"}, {".wdp", "image/vnd.ms-photo"}, {".webarchive", "application/x-safari-webarchive"}, {".webm", "video/webm"}, {".webp", "image/webp"}, /* https://en.wikipedia.org/wiki/WebP */ {".webtest", "application/xml"}, {".wiq", "application/xml"}, {".wiz", "application/msword"}, {".wks", "application/vnd.ms-works"}, {".WLMP", "application/wlmoviemaker"}, {".wlpginstall", "application/x-wlpg-detect"}, {".wlpginstall3", "application/x-wlpg3-detect"}, {".wm", "video/x-ms-wm"}, {".wma", "audio/x-ms-wma"}, {".wmd", "application/x-ms-wmd"}, {".wmf", "application/x-msmetafile"}, {".wml", "text/vnd.wap.wml"}, {".wmlc", "application/vnd.wap.wmlc"}, {".wmls", "text/vnd.wap.wmlscript"}, {".wmlsc", "application/vnd.wap.wmlscriptc"}, {".wmp", "video/x-ms-wmp"}, {".wmv", "video/x-ms-wmv"}, {".wmx", "video/x-ms-wmx"}, {".wmz", "application/x-ms-wmz"}, {".woff", "application/font-woff"}, {".wpl", "application/vnd.ms-wpl"}, {".wps", "application/vnd.ms-works"}, {".wri", "application/x-mswrite"}, {".wrl", "x-world/x-vrml"}, {".wrz", "x-world/x-vrml"}, {".wsc", "text/scriptlet"}, {".wsdl", "text/xml"}, {".wvx", "video/x-ms-wvx"}, {".x", "application/directx"}, {".xaf", "x-world/x-vrml"}, {".xaml", "application/xaml+xml"}, {".xap", "application/x-silverlight-app"}, {".xbap", "application/x-ms-xbap"}, {".xbm", "image/x-xbitmap"}, {".xdr", "text/plain"}, {".xht", "application/xhtml+xml"}, {".xhtml", "application/xhtml+xml"}, {".xla", "application/vnd.ms-excel"}, {".xlam", "application/vnd.ms-excel.addin.macroEnabled.12"}, {".xlc", "application/vnd.ms-excel"}, {".xld", "application/vnd.ms-excel"}, {".xlk", "application/vnd.ms-excel"}, {".xll", "application/vnd.ms-excel"}, {".xlm", "application/vnd.ms-excel"}, {".xls", "application/vnd.ms-excel"}, {".xlsb", "application/vnd.ms-excel.sheet.binary.macroEnabled.12"}, {".xlsm", "application/vnd.ms-excel.sheet.macroEnabled.12"}, {".xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"}, {".xlt", "application/vnd.ms-excel"}, {".xltm", "application/vnd.ms-excel.template.macroEnabled.12"}, {".xltx", "application/vnd.openxmlformats-officedocument.spreadsheetml.template"}, {".xlw", "application/vnd.ms-excel"}, {".xml", "text/xml"}, {".xmta", "application/xml"}, {".xof", "x-world/x-vrml"}, {".XOML", "text/plain"}, {".xpm", "image/x-xpixmap"}, {".xps", "application/vnd.ms-xpsdocument"}, {".xrm-ms", "text/xml"}, {".xsc", "application/xml"}, {".xsd", "text/xml"}, {".xsf", "text/xml"}, {".xsl", "text/xml"}, {".xslt", "text/xml"}, {".xsn", "application/octet-stream"}, {".xss", "application/xml"}, {".xspf", "application/xspf+xml"}, {".xtp", "application/octet-stream"}, {".xwd", "image/x-xwindowdump"}, {".z", "application/x-compress"}, {".zip", "application/zip"}, {"application/fsharp-script", ".fsx"}, {"application/msaccess", ".adp"}, {"application/msword", ".doc"}, {"application/octet-stream", ".bin"}, {"application/onenote", ".one"}, {"application/postscript", ".eps"}, {"application/step", ".step"}, {"application/vnd.ms-excel", ".xls"}, {"application/vnd.ms-powerpoint", ".ppt"}, {"application/vnd.ms-works", ".wks"}, {"application/vnd.visio", ".vsd"}, {"application/x-director", ".dir"}, {"application/x-shockwave-flash", ".swf"}, {"application/x-x509-ca-cert", ".cer"}, {"application/x-zip-compressed", ".zip"}, {"application/xhtml+xml", ".xhtml"}, {"application/xml", ".xml"}, // anomoly, .xml -> text/xml, but application/xml -> many thingss, but all are xml, so safest is .xml {"audio/aac", ".AAC"}, {"audio/aiff", ".aiff"}, {"audio/basic", ".snd"}, {"audio/mid", ".midi"}, {"audio/wav", ".wav"}, {"audio/x-m4a", ".m4a"}, {"audio/x-mpegurl", ".m3u"}, {"audio/x-pn-realaudio", ".ra"}, {"audio/x-smd", ".smd"}, {"image/bmp", ".bmp"}, {"image/jpeg", ".jpg"}, {"image/pict", ".pic"}, {"image/png", ".png"}, {"image/tiff", ".tiff"}, {"image/x-macpaint", ".mac"}, {"image/x-quicktime", ".qti"}, {"message/rfc822", ".eml"}, {"text/html", ".html"}, {"text/plain", ".txt"}, {"text/scriptlet", ".wsc"}, {"text/xml", ".xml"}, {"video/3gpp", ".3gp"}, {"video/3gpp2", ".3gp2"}, {"video/mp4", ".mp4"}, {"video/mpeg", ".mpg"}, {"video/quicktime", ".mov"}, {"video/vnd.dlna.mpeg-tts", ".m2t"}, {"video/x-dv", ".dv"}, {"video/x-la-asf", ".lsf"}, {"video/x-ms-asf", ".asf"}, {"x-world/x-vrml", ".xof"}, #endregion }; var cache = mappings.ToList(); // need ToList() to avoid modifying while still enumerating foreach (var mapping in cache) { if (!mappings.ContainsKey(mapping.Value)) { mappings.Add(mapping.Value, mapping.Key); } } return mappings; } public static string GetMimeType(string extension) { if (extension == null) { throw new ArgumentNullException("extension"); } if (!extension.StartsWith(".")) { extension = "." + extension; } string mime; return _mappings.Value.TryGetValue(extension, out mime) ? mime : "application/octet-stream"; } public static string GetExtension(string mimeType) { if (mimeType == null) { throw new ArgumentNullException("mimeType"); } if (mimeType.StartsWith(".")) { throw new ArgumentException("Requested mime type is not valid: " + mimeType); } string extension; if (_mappings.Value.TryGetValue(mimeType, out extension)) { return extension; } throw new ArgumentException("Requested mime type is not registered: " + mimeType); } } } |
Benché inevitabilmente prolisso, questo approccio risulta spesso molto più efficace e risolutivo del precedente. L'unico problema, ovviamente, è che trattandosi di una mappatura statica è necessario tenerla costantemente aggiornata man mano che nuovi MIME Type vengono definiti e/o rilasciati.
Fortunatamente l'autore del progetto ha pensato bene di creare un package NuGet costantemente aggiornato: è sufficiente aggiungerlo come dipendenza al nostro progetto ASP.NET per risolvere il problema una volta per tutte.
Un enorme ringraziamento a Samuel Neff per l'eccellente lavoro svolto!
UPDATE: il lettore Martino Bordin, che ringraziamo, ci avvisa che a partire dal framework 4.5 è finalmente stato aggiunto un metodo pubblico al namespace System.Web, denominato System.Web.GetMimeMapping, il quale consente di accedere al dictionary interno System.Web.MimeMapping - il quale contiene ben 342 MIME Type noti! Se utilizzate il framework 4.5 potete utilizzare questo metodo nativo e risparmiarvi ulteriori dipendenze o implementazioni ad-hoc, in caso contrario... Potete utilizzarlo lo stesso tramite le potenzialità del namespace System.Reflections come suggerito da questo eccellente post di David Haney, che - per chi non lo sapesse - è anche Engineering Manager di StackOverflow.
Ecco il codice della classe da lui pensata, denominata non a caso MimeMappingStealer, nella quale il dizionario viene esposto tramite Invoke all'interno di un metodo publlico:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 |
/// <summary> /// Exposes the Mime Mapping method that Microsoft hid from us. /// </summary> public static class MimeMappingStealer { // The get mime mapping method info private static readonly MethodInfo _getMimeMappingMethod = null; /// <summary> /// Static constructor sets up reflection. /// </summary> static MimeMappingStealer() { // Load hidden mime mapping class and method from System.Web var assembly = Assembly.GetAssembly(typeof(HttpApplication)); Type mimeMappingType = assembly.GetType("System.Web.MimeMapping"); _getMimeMappingMethod = mimeMappingType.GetMethod("GetMimeMapping", BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.FlattenHierarchy); } /// <summary> /// Exposes the hidden Mime mapping method. /// </summary> /// <param name="fileName">The file name.</param> /// <returns>The mime mapping.</returns> public static string GetMimeMapping(string fileName) { return (string)_getMimeMappingMethod.Invoke(null /*static method*/, new[] { fileName }); } } |
Un grazie finale a Martino e a David: alla prossima!
Volendo c’è anche una classe del framework: https://msdn.microsoft.com/it-it/library/system.web.mimemapping.getmimemapping(v=vs.110).aspx
Grazie mille, non ero al corrente che (finalmente) lo avessero reso pubblico! Ho aggiornato l’articolo menzionando il tuo suggerimento e (visto che c’ero) il contributo di David Haney per chi non avesse modo di aggiornare al framework 4.5: grazie ancora!
Di niente..non so quale delle 2 sia più completa, dovrei aprire l’assembly del framework ..quasi sicuramente quella del package comunque credo :)