MimeType

using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using Microsoft.Win32;

namespace System.Web {

    public static class MimeType {

        #region Mime extention type dictionary
        public static ConcurrentDictionary<string,string> Cache = new ConcurrentDictionary<string,string>(new Dictionary<string,string>
        {
            { ".323", "text/h323" },
            { ".asx", "video/x-ms-asf" },
            { ".acx", "application/internet-property-stream" },
            { ".ai", "application/postscript" },
            { ".aif", "audio/x-aiff" },
            { ".aiff", "audio/aiff" },
            { ".axs", "application/olescript" },
            { ".aifc", "audio/aiff" },
            { ".asr", "video/x-ms-asf" },
            { ".avi", "video/x-msvideo" },
            { ".asf", "video/x-ms-asf" },
            { ".au", "audio/basic" },
            { ".application", "application/x-ms-application" },
            { ".bin", "application/octet-stream" },
            { ".bas", "text/plain" },
            { ".bcpio", "application/x-bcpio" },
            { ".bmp", "image/bmp" },
            { ".cdf", "application/x-cdf" },
            { ".cat", "application/vndms-pkiseccat" },
            { ".crt", "application/x-x509-ca-cert" },
            { ".c", "text/plain" },
            { ".css", "text/css" },
            { ".cer", "application/x-x509-ca-cert" },
            { ".crl", "application/pkix-crl" },
            { ".cmx", "image/x-cmx" },
            { ".csh", "application/x-csh" },
            { ".cod", "image/cis-cod" },
            { ".cpio", "application/x-cpio" },
            { ".clp", "application/x-msclip" },
            { ".crd", "application/x-mscardfile" },
            { ".deploy", "application/octet-stream" },
            { ".dll", "application/x-msdownload" },
            { ".dot", "application/msword" },
            { ".doc", "application/msword" },
            { ".docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document" },
            { ".dotx", "application/vnd.openxmlformats-officedocument.wordprocessingml.template" },
            { ".docm", "application/vnd.ms-word.document.macroEnabled.12" },
            { ".dotm", "application/vnd.ms-word.template.macroEnabled.12" },
            { ".dvi", "application/x-dvi" },
            { ".dir", "application/x-director" },
            { ".dxr", "application/x-director" },
            { ".der", "application/x-x509-ca-cert" },
            { ".dib", "image/bmp" },
            { ".dcr", "application/x-director" },
            { ".disco", "text/xml" },
            { ".exe", "application/octet-stream" },
            { ".etx", "text/x-setext" },
            { ".evy", "application/envoy" },
            { ".eml", "message/rfc822" },
            { ".eps", "application/postscript" },
            { ".flr", "x-world/x-vrml" },
            { ".fif", "application/fractals" },
            { ".gtar", "application/x-gtar" },
            { ".gif", "image/gif" },
            { ".gz", "application/x-gzip" },
            { ".hta", "application/hta" },
            { ".htc", "text/x-component" },
            { ".htt", "text/webviewhtml" },
            { ".h", "text/plain" },
            { ".hdf", "application/x-hdf" },
            { ".hlp", "application/winhlp" },
            { ".html", "text/html" },
            { ".htm", "text/html" },
            { ".hqx", "application/mac-binhex40" },
            { ".isp", "application/x-internet-signup" },
            { ".iii", "application/x-iphone" },
            { ".ief", "image/ief" },
            { ".ivf", "video/x-ivf" },
            { ".ins", "application/x-internet-signup" },
            { ".ico", "image/x-icon" },
            { ".jpg", "image/jpeg" },
            { ".jfif", "image/pjpeg" },
            { ".jpe", "image/jpeg" },
            { ".jpeg", "image/jpeg" },
            { ".js", "application/x-javascript" },
            { ".lsx", "video/x-la-asf" },
            { ".latex", "application/x-latex" },
            { ".lsf", "video/x-la-asf" },
            { ".manifest", "application/x-ms-manifest" },
            { ".mhtml", "message/rfc822" },
            { ".mny", "application/x-msmoney" },
            { ".mht", "message/rfc822" },
            { ".mid", "audio/mid" },
            { ".mpv2", "video/mpeg" },
            { ".man", "application/x-troff-man" },
            { ".mvb", "application/x-msmediaview" },
            { ".mpeg", "video/mpeg" },
            { ".m3u", "audio/x-mpegurl" },
            { ".mdb", "application/x-msaccess" },
            { ".mpp", "application/vnd.ms-project" },
            { ".m1v", "video/mpeg" },
            { ".mpa", "video/mpeg" },
            { ".me", "application/x-troff-me" },
            { ".m13", "application/x-msmediaview" },
            { ".movie", "video/x-sgi-movie" },
            { ".m14", "application/x-msmediaview" },
            { ".mpe", "video/mpeg" },
            { ".mp2", "video/mpeg" },
            { ".mov", "video/quicktime" },
            { ".mp3", "audio/mpeg" },
            { ".mpg", "video/mpeg" },
            { ".ms", "application/x-troff-ms" },
            { ".nc", "application/x-netcdf" },
            { ".nws", "message/rfc822" },
            { ".oda", "application/oda" },
            { ".ods", "application/oleobject" },
            { ".pmc", "application/x-perfmon" },
            { ".p7r", "application/x-pkcs7-certreqresp" },
            { ".p7b", "application/x-pkcs7-certificates" },
            { ".p7s", "application/pkcs7-signature" },
            { ".pmw", "application/x-perfmon" },
            { ".ps", "application/postscript" },
            { ".p7c", "application/pkcs7-mime" },
            { ".pbm", "image/x-portable-bitmap" },
            { ".ppm", "image/x-portable-pixmap" },
            { ".pub", "application/x-mspublisher" },
            { ".pnm", "image/x-portable-anymap" },
            { ".pml", "application/x-perfmon" },
            { ".p10", "application/pkcs10" },
            { ".pfx", "application/x-pkcs12" },
            { ".p12", "application/x-pkcs12" },
            { ".pdf", "application/pdf" },
            { ".pps", "application/vnd.ms-powerpoint" },
            { ".p7m", "application/pkcs7-mime" },
            { ".pko", "application/vndms-pkipko" },
            { ".ppt", "application/vnd.ms-powerpoint" },
            { ".pmr", "application/x-perfmon" },
            { ".pma", "application/x-perfmon" },
            { ".pot", "application/vnd.ms-powerpoint" },
            { ".ppa", "application/vnd.ms-powerpoint" },
            { ".pptx", "application/vnd.openxmlformats-officedocument.presentationml.presentation" },
            { ".potx", "application/vnd.openxmlformats-officedocument.presentationml.template" },
            { ".ppsx", "application/vnd.openxmlformats-officedocument.presentationml.slideshow" },
            { ".ppam", "application/vnd.ms-powerpoint.addin.macroEnabled.12" },
            { ".pptm", "application/vnd.ms-powerpoint.presentation.macroEnabled.12" },
            { ".potm", "application/vnd.ms-powerpoint.presentation.macroEnabled.12" },
            { ".ppsm", "application/vnd.ms-powerpoint.slideshow.macroEnabled.12" },
            { ".prf", "application/pics-rules" },
            { ".pgm", "image/x-portable-graymap" },
            { ".qt", "video/quicktime" },
            { ".ra", "audio/x-pn-realaudio" },
            { ".rgb", "image/x-rgb" },
            { ".ram", "audio/x-pn-realaudio" },
            { ".rmi", "audio/mid" },
            { ".ras", "image/x-cmu-raster" },
            { ".roff", "application/x-troff" },
            { ".rtf", "application/rtf" },
            { ".rtx", "text/richtext" },
            { ".sv4crc", "application/x-sv4crc" },
            { ".spc", "application/x-pkcs7-certificates" },
            { ".setreg", "application/set-registration-initiation" },
            { ".snd", "audio/basic" },
            { ".stl", "application/vndms-pkistl" },
            { ".setpay", "application/set-payment-initiation" },
            { ".stm", "text/html" },
            { ".shar", "application/x-shar" },
            { ".sh", "application/x-sh" },
            { ".sit", "application/x-stuffit" },
            { ".spl", "application/futuresplash" },
            { ".sct", "text/scriptlet" },
            { ".scd", "application/x-msschedule" },
            { ".sst", "application/vndms-pkicertstore" },
            { ".src", "application/x-wais-source" },
            { ".sv4cpio", "application/x-sv4cpio" },
            { ".tex", "application/x-tex" },
            { ".tgz", "application/x-compressed" },
            { ".t", "application/x-troff" },
            { ".tar", "application/x-tar" },
            { ".tr", "application/x-troff" },
            { ".tif", "image/tiff" },
            { ".txt", "text/plain" },
            { ".texinfo", "application/x-texinfo" },
            { ".trm", "application/x-msterminal" },
            { ".tiff", "image/tiff" },
            { ".tcl", "application/x-tcl" },
            { ".texi", "application/x-texinfo" },
            { ".tsv", "text/tab-separated-values" },
            { ".ustar", "application/x-ustar" },
            { ".uls", "text/iuls" },
            { ".vcf", "text/x-vcard" },
            { ".wps", "application/vnd.ms-works" },
            { ".wav", "audio/wav" },
            { ".wrz", "x-world/x-vrml" },
            { ".wri", "application/x-mswrite" },
            { ".wks", "application/vnd.ms-works" },
            { ".wmf", "application/x-msmetafile" },
            { ".wcm", "application/vnd.ms-works" },
            { ".wrl", "x-world/x-vrml" },
            { ".wdb", "application/vnd.ms-works" },
            { ".wsdl", "text/xml" },
            { ".xml", "text/xml" },
            { ".xlm", "application/vnd.ms-excel" },
            { ".xaf", "x-world/x-vrml" },
            { ".xla", "application/vnd.ms-excel" },
            { ".xls", "application/vnd.ms-excel" },
            { ".xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" },
            { ".xltx", "application/vnd.openxmlformats-officedocument.spreadsheetml.template" },
            { ".xlsm", "application/vnd.ms-excel.sheet.macroEnabled.12" },
            { ".xltm", "application/vnd.ms-excel.template.macroEnabled.12" },
            { ".xlam", "application/vnd.ms-excel.addin.macroEnabled.12" },
            { ".xlsb", "application/vnd.ms-excel.sheet.binary.macroEnabled.12" },
            { ".xof", "x-world/x-vrml" },
            { ".xlt", "application/vnd.ms-excel" },
            { ".xlc", "application/vnd.ms-excel" },
            { ".xsl", "text/xml" },
            { ".xbm", "image/x-xbitmap" },
            { ".xlw", "application/vnd.ms-excel" },
            { ".xpm", "image/x-xpixmap" },
            { ".xwd", "image/x-xwindowdump" },
            { ".xsd", "text/xml" },
            { ".z", "application/x-compress" },
            { ".zip", "application/x-zip-compressed" },
        });

        #endregion

        public static string FromFileName(string fileName) {
            return FromExtension(Path.GetExtension(fileName));
        }

        public static string FromExtension(string extension) {
            extension = extension.ToLower();

            return Cache.GetOrAdd(extension,ext => {
                using(RegistryKey regKey = Registry.ClassesRoot.OpenSubKey(ext)) {
                    if(regKey != null && regKey.GetValue("Content Type") != null)
                        return regKey.GetValue("Content Type").ToString();
                }

                return "application/" + extension.Substring(1);
            });
        }
    }

}