finding the mime type of the file

=======================================

public string GetMimeType(string fileName)
{
string mimeType;

switch (System.IO.Path.GetExtension(fileName).ToLower())
{
case ".3dm": mimeType = "x-world/x-3dmf"; break;
case ".3dmf": mimeType = "x-world/x-3dmf"; break;
case ".a": mimeType = "application/octet-stream"; break;
case ".aab": mimeType = "application/x-authorware-bin"; break;
case ".aam": mimeType = "application/x-authorware-map"; break;
case ".aas": mimeType = "application/x-authorware-seg"; break;
case ".abc": mimeType = "text/vnd.abc"; break;
case ".acgi": mimeType = "text/html"; break;
case ".afl": mimeType = "video/animaflex"; break;
case ".ai": mimeType = "application/postscript"; break;
case ".aif": mimeType = "audio/aiff"; break;
case ".aifc": mimeType = "audio/aiff"; break;
case ".aiff": mimeType = "audio/aiff"; break;
case ".aim": mimeType = "application/x-aim"; break;
case ".aip": mimeType = "text/x-audiosoft-intra"; break;
case ".ani": mimeType = "application/x-navi-animation"; break;
case ".aos": mimeType = "application/x-nokia-9000-communicator-add-on-software"; break;
case ".aps": mimeType = "application/mime"; break;
case ".arc": mimeType = "application/octet-stream"; break;
case ".arj": mimeType = "application/arj"; break;
case ".art": mimeType = "image/x-jg"; break;
case ".asf": mimeType = "video/x-ms-asf"; break;
case ".asm": mimeType = "text/x-asm"; break;
case ".asp": mimeType = "text/asp"; break;
case ".asx": mimeType = "video/x-ms-asf"; break;
case ".au": mimeType = "audio/basic"; break;
case ".avi": mimeType = "video/avi"; break;
case ".avs": mimeType = "video/avs-video"; break;
case ".bcpio": mimeType = "application/x-bcpio"; break;
case ".bin": mimeType = "application/octet-stream"; break;
case ".bm": mimeType = "image/bmp"; break;
case ".bmp": mimeType = "image/bmp"; break;
case ".boo": mimeType = "application/book"; break;
case ".book": mimeType = "application/book"; break;
case ".boz": mimeType = "application/x-bzip2"; break;
case ".bsh": mimeType = "application/x-bsh"; break;
case ".bz": mimeType = "application/x-bzip"; break;
case ".bz2": mimeType = "application/x-bzip2"; break;
case ".c": mimeType = "text/plain"; break;
case ".c++": mimeType = "text/plain"; break;
case ".cat": mimeType = "application/vnd.ms-pki.seccat"; break;
case ".cc": mimeType = "text/plain"; break;
case ".ccad": mimeType = "application/clariscad"; break;
case ".cco": mimeType = "application/x-cocoa"; break;
case ".cdf": mimeType = "application/cdf"; break;
case ".cer": mimeType = "application/pkix-cert"; break;
case ".cha": mimeType = "application/x-chat"; break;
case ".chat": mimeType = "application/x-chat"; break;
case ".class": mimeType = "application/java"; break;
case ".com": mimeType = "application/octet-stream"; break;
case ".conf": mimeType = "text/plain"; break;
case ".cpio": mimeType = "application/x-cpio"; break;
case ".cpp": mimeType = "text/x-c"; break;
case ".cpt": mimeType = "application/x-cpt"; break;
case ".crl": mimeType = "application/pkcs-crl"; break;
case ".crt": mimeType = "application/pkix-cert"; break;
case ".csh": mimeType = "application/x-csh"; break;
case ".css": mimeType = "text/css"; break;
case ".cxx": mimeType = "text/plain"; break;
case ".dcr": mimeType = "application/x-director"; break;
case ".deepv": mimeType = "application/x-deepv"; break;
case ".def": mimeType = "text/plain"; break;
case ".der": mimeType = "application/x-x509-ca-cert"; break;
case ".dif": mimeType = "video/x-dv"; break;
case ".dir": mimeType = "application/x-director"; break;
case ".dl": mimeType = "video/dl"; break;
case ".doc": mimeType = "application/msword"; break;
case ".dot": mimeType = "application/msword"; break;
case ".dp": mimeType = "application/commonground"; break;
case ".drw": mimeType = "application/drafting"; break;
case ".dump": mimeType = "application/octet-stream"; break;
case ".dv": mimeType = "video/x-dv"; break;
case ".dvi": mimeType = "application/x-dvi"; break;
case ".dwf": mimeType = "model/vnd.dwf"; break;
case ".dwg": mimeType = "image/vnd.dwg"; break;
case ".dxf": mimeType = "image/vnd.dwg"; break;
case ".dxr": mimeType = "application/x-director"; break;
case ".el": mimeType = "text/x-script.elisp"; break;
case ".elc": mimeType = "application/x-elc"; break;
case ".env": mimeType = "application/x-envoy"; break;
case ".eps": mimeType = "application/postscript"; break;
case ".es": mimeType = "application/x-esrehber"; break;
case ".etx": mimeType = "text/x-setext"; break;
case ".evy": mimeType = "application/envoy"; break;
case ".exe": mimeType = "application/octet-stream"; break;
case ".f": mimeType = "text/plain"; break;
case ".f77": mimeType = "text/x-fortran"; break;
case ".f90": mimeType = "text/plain"; break;
case ".fdf": mimeType = "application/vnd.fdf"; break;
case ".fif": mimeType = "image/fif"; break;
case ".fli": mimeType = "video/fli"; break;
case ".flo": mimeType = "image/florian"; break;
case ".flx": mimeType = "text/vnd.fmi.flexstor"; break;
case ".fmf": mimeType = "video/x-atomic3d-feature"; break;
case ".for": mimeType = "text/x-fortran"; break;
case ".fpx": mimeType = "image/vnd.fpx"; break;
case ".frl": mimeType = "application/freeloader"; break;
case ".funk": mimeType = "audio/make"; break;
case ".g": mimeType = "text/plain"; break;
case ".g3": mimeType = "image/g3fax"; break;
case ".gif": mimeType = "image/gif"; break;
case ".gl": mimeType = "video/gl"; break;
case ".gsd": mimeType = "audio/x-gsm"; break;
case ".gsm": mimeType = "audio/x-gsm"; break;
case ".gsp": mimeType = "application/x-gsp"; break;
case ".gss": mimeType = "application/x-gss"; break;
case ".gtar": mimeType = "application/x-gtar"; break;
case ".gz": mimeType = "application/x-gzip"; break;
case ".gzip": mimeType = "application/x-gzip"; break;
case ".h": mimeType = "text/plain"; break;
case ".hdf": mimeType = "application/x-hdf"; break;
case ".help": mimeType = "application/x-helpfile"; break;
case ".hgl": mimeType = "application/vnd.hp-hpgl"; break;
case ".hh": mimeType = "text/plain"; break;
case ".hlb": mimeType = "text/x-script"; break;
case ".hlp": mimeType = "application/hlp"; break;
case ".hpg": mimeType = "application/vnd.hp-hpgl"; break;
case ".hpgl": mimeType = "application/vnd.hp-hpgl"; break;
case ".hqx": mimeType = "application/binhex"; break;
case ".hta": mimeType = "application/hta"; break;
case ".htc": mimeType = "text/x-component"; break;
case ".htm": mimeType = "text/html"; break;
case ".html": mimeType = "text/html"; break;
case ".htmls": mimeType = "text/html"; break;
case ".htt": mimeType = "text/webviewhtml"; break;
case ".htx": mimeType = "text/html"; break;
case ".ice": mimeType = "x-conference/x-cooltalk"; break;
case ".ico": mimeType = "image/x-icon"; break;
case ".idc": mimeType = "text/plain"; break;
case ".ief": mimeType = "image/ief"; break;
case ".iefs": mimeType = "image/ief"; break;
case ".iges": mimeType = "application/iges"; break;
case ".igs": mimeType = "application/iges"; break;
case ".ima": mimeType = "application/x-ima"; break;
case ".imap": mimeType = "application/x-httpd-imap"; break;
case ".inf": mimeType = "application/inf"; break;
case ".ins": mimeType = "application/x-internett-signup"; break;
case ".ip": mimeType = "application/x-ip2"; break;
case ".isu": mimeType = "video/x-isvideo"; break;
case ".it": mimeType = "audio/it"; break;
case ".iv": mimeType = "application/x-inventor"; break;
case ".ivr": mimeType = "i-world/i-vrml"; break;
case ".ivy": mimeType = "application/x-livescreen"; break;
case ".jam": mimeType = "audio/x-jam"; break;
case ".jav": mimeType = "text/plain"; break;
case ".java": mimeType = "text/plain"; break;
case ".jcm": mimeType = "application/x-java-commerce"; break;
case ".jfif": mimeType = "image/jpeg"; break;
case ".jfif-tbnl": mimeType = "image/jpeg"; break;
case ".jpe": mimeType = "image/jpeg"; break;
case ".jpeg": mimeType = "image/jpeg"; break;
case ".jpg": mimeType = "image/jpeg"; break;
case ".jps": mimeType = "image/x-jps"; break;
case ".js": mimeType = "application/x-javascript"; break;
case ".jut": mimeType = "image/jutvision"; break;
case ".kar": mimeType = "audio/midi"; break;
case ".ksh": mimeType = "application/x-ksh"; break;
case ".la": mimeType = "audio/nspaudio"; break;
case ".lam": mimeType = "audio/x-liveaudio"; break;
case ".latex": mimeType = "application/x-latex"; break;
case ".lha": mimeType = "application/octet-stream"; break;
case ".lhx": mimeType = "application/octet-stream"; break;
case ".list": mimeType = "text/plain"; break;
case ".lma": mimeType = "audio/nspaudio"; break;
case ".log": mimeType = "text/plain"; break;
case ".lsp": mimeType = "application/x-lisp"; break;
case ".lst": mimeType = "text/plain"; break;
case ".lsx": mimeType = "text/x-la-asf"; break;
case ".ltx": mimeType = "application/x-latex"; break;
case ".lzh": mimeType = "application/octet-stream"; break;
case ".lzx": mimeType = "application/octet-stream"; break;
case ".m": mimeType = "text/plain"; break;
case ".m1v": mimeType = "video/mpeg"; break;
case ".m2a": mimeType = "audio/mpeg"; break;
case ".m2v": mimeType = "video/mpeg"; break;
case ".m3u": mimeType = "audio/x-mpequrl"; break;
case ".man": mimeType = "application/x-troff-man"; break;
case ".map": mimeType = "application/x-navimap"; break;
case ".mar": mimeType = "text/plain"; break;
case ".mbd": mimeType = "application/mbedlet"; break;
case ".mc$": mimeType = "application/x-magic-cap-package-1.0"; break;
case ".mcd": mimeType = "application/mcad"; break;
case ".mcf": mimeType = "text/mcf"; break;
case ".mcp": mimeType = "application/netmc"; break;
case ".me": mimeType = "application/x-troff-me"; break;
case ".mht": mimeType = "message/rfc822"; break;
case ".mhtml": mimeType = "message/rfc822"; break;
case ".mid": mimeType = "audio/midi"; break;
case ".midi": mimeType = "audio/midi"; break;
case ".mif": mimeType = "application/x-mif"; break;
case ".mime": mimeType = "message/rfc822"; break;
case ".mjf": mimeType = "audio/x-vnd.audioexplosion.mjuicemediafile"; break;
case ".mjpg": mimeType = "video/x-motion-jpeg"; break;
case ".mm": mimeType = "application/base64"; break;
case ".mme": mimeType = "application/base64"; break;
case ".mod": mimeType = "audio/mod"; break;
case ".moov": mimeType = "video/quicktime"; break;
case ".mov": mimeType = "video/quicktime"; break;
case ".movie": mimeType = "video/x-sgi-movie"; break;
case ".mp2": mimeType = "audio/mpeg"; break;
case ".mp3": mimeType = "audio/mpeg"; break;
case ".mpa": mimeType = "audio/mpeg"; break;
case ".mpc": mimeType = "application/x-project"; break;
case ".mpe": mimeType = "video/mpeg"; break;
case ".mpeg": mimeType = "video/mpeg"; break;
case ".mpg": mimeType = "video/mpeg"; break;
case ".mpga": mimeType = "audio/mpeg"; break;
case ".mpp": mimeType = "application/vnd.ms-project"; break;
case ".mpt": mimeType = "application/vnd.ms-project"; break;
case ".mpv": mimeType = "application/vnd.ms-project"; break;
case ".mpx": mimeType = "application/vnd.ms-project"; break;
case ".mrc": mimeType = "application/marc"; break;
case ".ms": mimeType = "application/x-troff-ms"; break;
case ".mv": mimeType = "video/x-sgi-movie"; break;
case ".my": mimeType = "audio/make"; break;
case ".mzz": mimeType = "application/x-vnd.audioexplosion.mzz"; break;
case ".nap": mimeType = "image/naplps"; break;
case ".naplps": mimeType = "image/naplps"; break;
case ".nc": mimeType = "application/x-netcdf"; break;
case ".ncm": mimeType = "application/vnd.nokia.configuration-message"; break;
case ".nif": mimeType = "image/x-niff"; break;
case ".niff": mimeType = "image/x-niff"; break;
case ".nix": mimeType = "application/x-mix-transfer"; break;
case ".nsc": mimeType = "application/x-conference"; break;
case ".nvd": mimeType = "application/x-navidoc"; break;
case ".o": mimeType = "application/octet-stream"; break;
case ".oda": mimeType = "application/oda"; break;
case ".omc": mimeType = "application/x-omc"; break;
case ".omcd": mimeType = "application/x-omcdatamaker"; break;
case ".omcr": mimeType = "application/x-omcregerator"; break;
case ".p": mimeType = "text/x-pascal"; break;
case ".p10": mimeType = "application/pkcs10"; break;
case ".p12": mimeType = "application/pkcs-12"; break;
case ".p7a": mimeType = "application/x-pkcs7-signature"; break;
case ".p7c": mimeType = "application/pkcs7-mime"; break;
case ".p7m": mimeType = "application/pkcs7-mime"; break;
case ".p7r": mimeType = "application/x-pkcs7-certreqresp"; break;
case ".p7s": mimeType = "application/pkcs7-signature"; break;
case ".part": mimeType = "application/pro_eng"; break;
case ".pas": mimeType = "text/pascal"; break;
case ".pbm": mimeType = "image/x-portable-bitmap"; break;
case ".pcl": mimeType = "application/vnd.hp-pcl"; break;
case ".pct": mimeType = "image/x-pict"; break;
case ".pcx": mimeType = "image/x-pcx"; break;
case ".pdb": mimeType = "chemical/x-pdb"; break;
case ".pdf": mimeType = "application/pdf"; break;
case ".pfunk": mimeType = "audio/make"; break;
case ".pgm": mimeType = "image/x-portable-greymap"; break;
case ".pic": mimeType = "image/pict"; break;
case ".pict": mimeType = "image/pict"; break;
case ".pkg": mimeType = "application/x-newton-compatible-pkg"; break;
case ".pko": mimeType = "application/vnd.ms-pki.pko"; break;
case ".pl": mimeType = "text/plain"; break;
case ".plx": mimeType = "application/x-pixclscript"; break;
case ".pm": mimeType = "image/x-xpixmap"; break;
case ".pm4": mimeType = "application/x-pagemaker"; break;
case ".pm5": mimeType = "application/x-pagemaker"; break;
case ".png": mimeType = "image/png"; break;
case ".pnm": mimeType = "application/x-portable-anymap"; break;
case ".pot": mimeType = "application/vnd.ms-powerpoint"; break;
case ".pov": mimeType = "model/x-pov"; break;
case ".ppa": mimeType = "application/vnd.ms-powerpoint"; break;
case ".ppm": mimeType = "image/x-portable-pixmap"; break;
case ".pps": mimeType = "application/vnd.ms-powerpoint"; break;
case ".ppt": mimeType = "application/vnd.ms-powerpoint"; break;
case ".ppz": mimeType = "application/vnd.ms-powerpoint"; break;
case ".pre": mimeType = "application/x-freelance"; break;
case ".prt": mimeType = "application/pro_eng"; break;
case ".ps": mimeType = "application/postscript"; break;
case ".psd": mimeType = "application/octet-stream"; break;
case ".pvu": mimeType = "paleovu/x-pv"; break;
case ".pwz": mimeType = "application/vnd.ms-powerpoint"; break;
case ".py": mimeType = "text/x-script.phyton"; break;
case ".pyc": mimeType = "applicaiton/x-bytecode.python"; break;
case ".qcp": mimeType = "audio/vnd.qcelp"; break;
case ".qd3": mimeType = "x-world/x-3dmf"; break;
case ".qd3d": mimeType = "x-world/x-3dmf"; break;
case ".qif": mimeType = "image/x-quicktime"; break;
case ".qt": mimeType = "video/quicktime"; break;
case ".qtc": mimeType = "video/x-qtc"; break;
case ".qti": mimeType = "image/x-quicktime"; break;
case ".qtif": mimeType = "image/x-quicktime"; break;
case ".ra": mimeType = "audio/x-pn-realaudio"; break;
case ".ram": mimeType = "audio/x-pn-realaudio"; break;
case ".ras": mimeType = "application/x-cmu-raster"; break;
case ".rast": mimeType = "image/cmu-raster"; break;
case ".rexx": mimeType = "text/x-script.rexx"; break;
case ".rf": mimeType = "image/vnd.rn-realflash"; break;
case ".rgb": mimeType = "image/x-rgb"; break;
case ".rm": mimeType = "application/vnd.rn-realmedia"; break;
case ".rmi": mimeType = "audio/mid"; break;
case ".rmm": mimeType = "audio/x-pn-realaudio"; break;
case ".rmp": mimeType = "audio/x-pn-realaudio"; break;
case ".rng": mimeType = "application/ringing-tones"; break;
case ".rnx": mimeType = "application/vnd.rn-realplayer"; break;
case ".roff": mimeType = "application/x-troff"; break;
case ".rp": mimeType = "image/vnd.rn-realpix"; break;
case ".rpm": mimeType = "audio/x-pn-realaudio-plugin"; break;
case ".rt": mimeType = "text/richtext"; break;
case ".rtf": mimeType = "text/richtext"; break;
case ".rtx": mimeType = "text/richtext"; break;
case ".rv": mimeType = "video/vnd.rn-realvideo"; break;
case ".s": mimeType = "text/x-asm"; break;
case ".s3m": mimeType = "audio/s3m"; break;
case ".saveme": mimeType = "application/octet-stream"; break;
case ".sbk": mimeType = "application/x-tbook"; break;
case ".scm": mimeType = "application/x-lotusscreencam"; break;
case ".sdml": mimeType = "text/plain"; break;
case ".sdp": mimeType = "application/sdp"; break;
case ".sdr": mimeType = "application/sounder"; break;
case ".sea": mimeType = "application/sea"; break;
case ".set": mimeType = "application/set"; break;
case ".sgm": mimeType = "text/sgml"; break;
case ".sgml": mimeType = "text/sgml"; break;
case ".sh": mimeType = "application/x-sh"; break;
case ".shar": mimeType = "application/x-shar"; break;
case ".shtml": mimeType = "text/html"; break;
case ".sid": mimeType = "audio/x-psid"; break;
case ".sit": mimeType = "application/x-sit"; break;
case ".skd": mimeType = "application/x-koan"; break;
case ".skm": mimeType = "application/x-koan"; break;
case ".skp": mimeType = "application/x-koan"; break;
case ".skt": mimeType = "application/x-koan"; break;
case ".sl": mimeType = "application/x-seelogo"; break;
case ".smi": mimeType = "application/smil"; break;
case ".smil": mimeType = "application/smil"; break;
case ".snd": mimeType = "audio/basic"; break;
case ".sol": mimeType = "application/solids"; break;
case ".spc": mimeType = "text/x-speech"; break;
case ".spl": mimeType = "application/futuresplash"; break;
case ".spr": mimeType = "application/x-sprite"; break;
case ".sprite": mimeType = "application/x-sprite"; break;
case ".src": mimeType = "application/x-wais-source"; break;
case ".ssi": mimeType = "text/x-server-parsed-html"; break;
case ".ssm": mimeType = "application/streamingmedia"; break;
case ".sst": mimeType = "application/vnd.ms-pki.certstore"; break;
case ".step": mimeType = "application/step"; break;
case ".stl": mimeType = "application/sla"; break;
case ".stp": mimeType = "application/step"; break;
case ".sv4cpio": mimeType = "application/x-sv4cpio"; break;
case ".sv4crc": mimeType = "application/x-sv4crc"; break;
case ".svf": mimeType = "image/vnd.dwg"; break;
case ".svr": mimeType = "application/x-world"; break;
case ".swf": mimeType = "application/x-shockwave-flash"; break;
case ".t": mimeType = "application/x-troff"; break;
case ".talk": mimeType = "text/x-speech"; break;
case ".tar": mimeType = "application/x-tar"; break;
case ".tbk": mimeType = "application/toolbook"; break;
case ".tcl": mimeType = "application/x-tcl"; break;
case ".tcsh": mimeType = "text/x-script.tcsh"; break;
case ".tex": mimeType = "application/x-tex"; break;
case ".texi": mimeType = "application/x-texinfo"; break;
case ".texinfo": mimeType = "application/x-texinfo"; break;
case ".text": mimeType = "text/plain"; break;
case ".tgz": mimeType = "application/x-compressed"; break;
case ".tif": mimeType = "image/tiff"; break;
case ".tiff": mimeType = "image/tiff"; break;
case ".tr": mimeType = "application/x-troff"; break;
case ".tsi": mimeType = "audio/tsp-audio"; break;
case ".tsp": mimeType = "application/dsptype"; break;
case ".tsv": mimeType = "text/tab-separated-values"; break;
case ".turbot": mimeType = "image/florian"; break;
case ".txt": mimeType = "text/plain"; break;
case ".uil": mimeType = "text/x-uil"; break;
case ".uni": mimeType = "text/uri-list"; break;
case ".unis": mimeType = "text/uri-list"; break;
case ".unv": mimeType = "application/i-deas"; break;
case ".uri": mimeType = "text/uri-list"; break;
case ".uris": mimeType = "text/uri-list"; break;
case ".ustar": mimeType = "application/x-ustar"; break;
case ".uu": mimeType = "application/octet-stream"; break;
case ".uue": mimeType = "text/x-uuencode"; break;
case ".vcd": mimeType = "application/x-cdlink"; break;
case ".vcs": mimeType = "text/x-vcalendar"; break;
case ".vda": mimeType = "application/vda"; break;
case ".vdo": mimeType = "video/vdo"; break;
case ".vew": mimeType = "application/groupwise"; break;
case ".viv": mimeType = "video/vivo"; break;
case ".vivo": mimeType = "video/vivo"; break;
case ".vmd": mimeType = "application/vocaltec-media-desc"; break;
case ".vmf": mimeType = "application/vocaltec-media-file"; break;
case ".voc": mimeType = "audio/voc"; break;
case ".vos": mimeType = "video/vosaic"; break;
case ".vox": mimeType = "audio/voxware"; break;
case ".vqe": mimeType = "audio/x-twinvq-plugin"; break;
case ".vqf": mimeType = "audio/x-twinvq"; break;
case ".vql": mimeType = "audio/x-twinvq-plugin"; break;
case ".vrml": mimeType = "application/x-vrml"; break;
case ".vrt": mimeType = "x-world/x-vrt"; break;
case ".vsd": mimeType = "application/x-visio"; break;
case ".vst": mimeType = "application/x-visio"; break;
case ".vsw": mimeType = "application/x-visio"; break;
case ".w60": mimeType = "application/wordperfect6.0"; break;
case ".w61": mimeType = "application/wordperfect6.1"; break;
case ".w6w": mimeType = "application/msword"; break;
case ".wav": mimeType = "audio/wav"; break;
case ".wb1": mimeType = "application/x-qpro"; break;
case ".wbmp": mimeType = "image/vnd.wap.wbmp"; break;
case ".web": mimeType = "application/vnd.xara"; break;
case ".wiz": mimeType = "application/msword"; break;
case ".wk1": mimeType = "application/x-123"; break;
case ".wmf": mimeType = "windows/metafile"; break;
case ".wml": mimeType = "text/vnd.wap.wml"; break;
case ".wmlc": mimeType = "application/vnd.wap.wmlc"; break;
case ".wmls": mimeType = "text/vnd.wap.wmlscript"; break;
case ".wmlsc": mimeType = "application/vnd.wap.wmlscriptc"; break;
case ".word": mimeType = "application/msword"; break;
case ".wp": mimeType = "application/wordperfect"; break;
case ".wp5": mimeType = "application/wordperfect"; break;
case ".wp6": mimeType = "application/wordperfect"; break;
case ".wpd": mimeType = "application/wordperfect"; break;
case ".wq1": mimeType = "application/x-lotus"; break;
case ".wri": mimeType = "application/mswrite"; break;
case ".wrl": mimeType = "application/x-world"; break;
case ".wrz": mimeType = "x-world/x-vrml"; break;
case ".wsc": mimeType = "text/scriplet"; break;
case ".wsrc": mimeType = "application/x-wais-source"; break;
case ".wtk": mimeType = "application/x-wintalk"; break;
case ".xbm": mimeType = "image/x-xbitmap"; break;
case ".xdr": mimeType = "video/x-amt-demorun"; break;
case ".xgz": mimeType = "xgl/drawing"; break;
case ".xif": mimeType = "image/vnd.xiff"; break;
case ".xl": mimeType = "application/excel"; break;
case ".xla": mimeType = "application/vnd.ms-excel"; break;
case ".xlb": mimeType = "application/vnd.ms-excel"; break;
case ".xlc": mimeType = "application/vnd.ms-excel"; break;
case ".xld": mimeType = "application/vnd.ms-excel"; break;
case ".xlk": mimeType = "application/vnd.ms-excel"; break;
case ".xll": mimeType = "application/vnd.ms-excel"; break;
case ".xlm": mimeType = "application/vnd.ms-excel"; break;
case ".xls": mimeType = "application/vnd.ms-excel"; break;
case ".xlt": mimeType = "application/vnd.ms-excel"; break;
case ".xlv": mimeType = "application/vnd.ms-excel"; break;
case ".xlw": mimeType = "application/vnd.ms-excel"; break;
case ".xm": mimeType = "audio/xm"; break;
case ".xml": mimeType = "application/xml"; break;
case ".xmz": mimeType = "xgl/movie"; break;
case ".xpix": mimeType = "application/x-vnd.ls-xpix"; break;
case ".xpm": mimeType = "image/xpm"; break;
case ".x-png": mimeType = "image/png"; break;
case ".xsr": mimeType = "video/x-amt-showrun"; break;
case ".xwd": mimeType = "image/x-xwd"; break;
case ".xyz": mimeType = "chemical/x-pdb"; break;
case ".z": mimeType = "application/x-compressed"; break;
case ".zip": mimeType = "application/zip"; break;
case ".zoo": mimeType = "application/octet-stream"; break;
case ".zsh": mimeType = "text/x-script.zsh"; break;
default: mimeType = "application/octet-stream"; break;
}
return mimeType;
}


---- another way ------
=====================================================================================
public string GetMimeType(string fileName)
{
string mimeType = "application/unknown";
string ext = System.IO.Path.GetExtension(fileName).ToLower();
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;
}

=======================================================================================