当然，为了将通用完整性、动态性和可移植性的优势与最小的依赖性结合起来

你将结合Samuel Neff的静态字典与特定平台的查询，例如由Bryan Denny。

例如，在Linux下，命令行工具“xdg-mime”可以完成后面的部分。

你可以使用这个helper函数:

private 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;
}

由文件扩展名计算的mime类型不一定总是正确的。

让我们说，我可以保存一个文件的。png扩展名，但文件格式，我可以设置为“ImageFormat.jpeg”。

所以在这种情况下，你要计算的文件会给出不同的结果…这可能会导致文件比原始文件大。

如果你正在处理图像，那么你可以使用imagecodecInfo和ImageFormat。

您可以在注册表中找到这些信息。例如，.pdf文件的MIME类型可以在键HKEY_CLASSES_ROOT\.pdf中找到，在值"Content type "中:

string mimeType = Registry.GetValue(@"HKEY_CLASSES_ROOT\.pdf", "Content Type", null) as string;

我喜欢Samuel Neff所做的工作，但不喜欢每次创建字典的想法和开销。

我把它重组成一个开关案例。是的，你不能迭代它，但在我的情况下，我只使用它来快速查找一个值。特别是因为它是在web服务中完成的，所以我最不希望的就是在应用程序准备其结构时产生大量开销。编译器会把这个转换成散列查找，所以会非常快。

public static string GetMimeType(string extension)
{
  if (extension == null)
    throw new ArgumentNullException("extension");

  if (extension.StartsWith("."))
    extension = extension.Substring(1);


  switch (extension.ToLower())
{
    #region Big freaking list of mime types
    case "323": return "text/h323";
    case "3g2": return "video/3gpp2";
    case "3gp": return "video/3gpp";
    case "3gp2": return "video/3gpp2";
    case "3gpp": return "video/3gpp";
    case "7z": return "application/x-7z-compressed";
    case "aa": return "audio/audible";
    case "aac": return "audio/aac";
    case "aaf": return "application/octet-stream";
    case "aax": return "audio/vnd.audible.aax";
    case "ac3": return "audio/ac3";
    case "aca": return "application/octet-stream";
    case "accda": return "application/msaccess.addin";
    case "accdb": return "application/msaccess";
    case "accdc": return "application/msaccess.cab";
    case "accde": return "application/msaccess";
    case "accdr": return "application/msaccess.runtime";
    case "accdt": return "application/msaccess";
    case "accdw": return "application/msaccess.webapplication";
    case "accft": return "application/msaccess.ftemplate";
    case "acx": return "application/internet-property-stream";
    case "addin": return "text/xml";
    case "ade": return "application/msaccess";
    case "adobebridge": return "application/x-bridge-url";
    case "adp": return "application/msaccess";
    case "adt": return "audio/vnd.dlna.adts";
    case "adts": return "audio/aac";
    case "afm": return "application/octet-stream";
    case "ai": return "application/postscript";
    case "aif": return "audio/x-aiff";
    case "aifc": return "audio/aiff";
    case "aiff": return "audio/aiff";
    case "air": return "application/vnd.adobe.air-application-installer-package+zip";
    case "amc": return "application/x-mpeg";
    case "application": return "application/x-ms-application";
    case "art": return "image/x-jg";
    case "asa": return "application/xml";
    case "asax": return "application/xml";
    case "ascx": return "application/xml";
    case "asd": return "application/octet-stream";
    case "asf": return "video/x-ms-asf";
    case "ashx": return "application/xml";
    case "asi": return "application/octet-stream";
    case "asm": return "text/plain";
    case "asmx": return "application/xml";
    case "aspx": return "application/xml";
    case "asr": return "video/x-ms-asf";
    case "asx": return "video/x-ms-asf";
    case "atom": return "application/atom+xml";
    case "au": return "audio/basic";
    case "avi": return "video/x-msvideo";
    case "axs": return "application/olescript";
    case "bas": return "text/plain";
    case "bcpio": return "application/x-bcpio";
    case "bin": return "application/octet-stream";
    case "bmp": return "image/bmp";
    case "c": return "text/plain";
    case "cab": return "application/octet-stream";
    case "caf": return "audio/x-caf";
    case "calx": return "application/vnd.ms-office.calx";
    case "cat": return "application/vnd.ms-pki.seccat";
    case "cc": return "text/plain";
    case "cd": return "text/plain";
    case "cdda": return "audio/aiff";
    case "cdf": return "application/x-cdf";
    case "cer": return "application/x-x509-ca-cert";
    case "chm": return "application/octet-stream";
    case "class": return "application/x-java-applet";
    case "clp": return "application/x-msclip";
    case "cmx": return "image/x-cmx";
    case "cnf": return "text/plain";
    case "cod": return "image/cis-cod";
    case "config": return "application/xml";
    case "contact": return "text/x-ms-contact";
    case "coverage": return "application/xml";
    case "cpio": return "application/x-cpio";
    case "cpp": return "text/plain";
    case "crd": return "application/x-mscardfile";
    case "crl": return "application/pkix-crl";
    case "crt": return "application/x-x509-ca-cert";
    case "cs": return "text/plain";
    case "csdproj": return "text/plain";
    case "csh": return "application/x-csh";
    case "csproj": return "text/plain";
    case "css": return "text/css";
    case "csv": return "text/csv";
    case "cur": return "application/octet-stream";
    case "cxx": return "text/plain";
    case "dat": return "application/octet-stream";
    case "datasource": return "application/xml";
    case "dbproj": return "text/plain";
    case "dcr": return "application/x-director";
    case "def": return "text/plain";
    case "deploy": return "application/octet-stream";
    case "der": return "application/x-x509-ca-cert";
    case "dgml": return "application/xml";
    case "dib": return "image/bmp";
    case "dif": return "video/x-dv";
    case "dir": return "application/x-director";
    case "disco": return "text/xml";
    case "dll": return "application/x-msdownload";
    case "dll.config": return "text/xml";
    case "dlm": return "text/dlm";
    case "doc": return "application/msword";
    case "docm": return "application/vnd.ms-word.document.macroenabled.12";
    case "docx": return "application/vnd.openxmlformats-officedocument.wordprocessingml.document";
    case "dot": return "application/msword";
    case "dotm": return "application/vnd.ms-word.template.macroenabled.12";
    case "dotx": return "application/vnd.openxmlformats-officedocument.wordprocessingml.template";
    case "dsp": return "application/octet-stream";
    case "dsw": return "text/plain";
    case "dtd": return "text/xml";
    case "dtsconfig": return "text/xml";
    case "dv": return "video/x-dv";
    case "dvi": return "application/x-dvi";
    case "dwf": return "drawing/x-dwf";
    case "dwp": return "application/octet-stream";
    case "dxr": return "application/x-director";
    case "eml": return "message/rfc822";
    case "emz": return "application/octet-stream";
    case "eot": return "application/octet-stream";
    case "eps": return "application/postscript";
    case "etl": return "application/etl";
    case "etx": return "text/x-setext";
    case "evy": return "application/envoy";
    case "exe": return "application/octet-stream";
    case "exe.config": return "text/xml";
    case "fdf": return "application/vnd.fdf";
    case "fif": return "application/fractals";
    case "filters": return "application/xml";
    case "fla": return "application/octet-stream";
    case "flr": return "x-world/x-vrml";
    case "flv": return "video/x-flv";
    case "fsscript": return "application/fsharp-script";
    case "fsx": return "application/fsharp-script";
    case "generictest": return "application/xml";
    case "gif": return "image/gif";
    case "group": return "text/x-ms-group";
    case "gsm": return "audio/x-gsm";
    case "gtar": return "application/x-gtar";
    case "gz": return "application/x-gzip";
    case "h": return "text/plain";
    case "hdf": return "application/x-hdf";
    case "hdml": return "text/x-hdml";
    case "hhc": return "application/x-oleobject";
    case "hhk": return "application/octet-stream";
    case "hhp": return "application/octet-stream";
    case "hlp": return "application/winhlp";
    case "hpp": return "text/plain";
    case "hqx": return "application/mac-binhex40";
    case "hta": return "application/hta";
    case "htc": return "text/x-component";
    case "htm": return "text/html";
    case "html": return "text/html";
    case "htt": return "text/webviewhtml";
    case "hxa": return "application/xml";
    case "hxc": return "application/xml";
    case "hxd": return "application/octet-stream";
    case "hxe": return "application/xml";
    case "hxf": return "application/xml";
    case "hxh": return "application/octet-stream";
    case "hxi": return "application/octet-stream";
    case "hxk": return "application/xml";
    case "hxq": return "application/octet-stream";
    case "hxr": return "application/octet-stream";
    case "hxs": return "application/octet-stream";
    case "hxt": return "text/html";
    case "hxv": return "application/xml";
    case "hxw": return "application/octet-stream";
    case "hxx": return "text/plain";
    case "i": return "text/plain";
    case "ico": return "image/x-icon";
    case "ics": return "application/octet-stream";
    case "idl": return "text/plain";
    case "ief": return "image/ief";
    case "iii": return "application/x-iphone";
    case "inc": return "text/plain";
    case "inf": return "application/octet-stream";
    case "inl": return "text/plain";
    case "ins": return "application/x-internet-signup";
    case "ipa": return "application/x-itunes-ipa";
    case "ipg": return "application/x-itunes-ipg";
    case "ipproj": return "text/plain";
    case "ipsw": return "application/x-itunes-ipsw";
    case "iqy": return "text/x-ms-iqy";
    case "isp": return "application/x-internet-signup";
    case "ite": return "application/x-itunes-ite";
    case "itlp": return "application/x-itunes-itlp";
    case "itms": return "application/x-itunes-itms";
    case "itpc": return "application/x-itunes-itpc";
    case "ivf": return "video/x-ivf";
    case "jar": return "application/java-archive";
    case "java": return "application/octet-stream";
    case "jck": return "application/liquidmotion";
    case "jcz": return "application/liquidmotion";
    case "jfif": return "image/pjpeg";
    case "jnlp": return "application/x-java-jnlp-file";
    case "jpb": return "application/octet-stream";
    case "jpe": return "image/jpeg";
    case "jpeg": return "image/jpeg";
    case "jpg": return "image/jpeg";
    case "js": return "application/x-javascript";
    case "jsx": return "text/jscript";
    case "jsxbin": return "text/plain";
    case "latex": return "application/x-latex";
    case "library-ms": return "application/windows-library+xml";
    case "lit": return "application/x-ms-reader";
    case "loadtest": return "application/xml";
    case "lpk": return "application/octet-stream";
    case "lsf": return "video/x-la-asf";
    case "lst": return "text/plain";
    case "lsx": return "video/x-la-asf";
    case "lzh": return "application/octet-stream";
    case "m13": return "application/x-msmediaview";
    case "m14": return "application/x-msmediaview";
    case "m1v": return "video/mpeg";
    case "m2t": return "video/vnd.dlna.mpeg-tts";
    case "m2ts": return "video/vnd.dlna.mpeg-tts";
    case "m2v": return "video/mpeg";
    case "m3u": return "audio/x-mpegurl";
    case "m3u8": return "audio/x-mpegurl";
    case "m4a": return "audio/m4a";
    case "m4b": return "audio/m4b";
    case "m4p": return "audio/m4p";
    case "m4r": return "audio/x-m4r";
    case "m4v": return "video/x-m4v";
    case "mac": return "image/x-macpaint";
    case "mak": return "text/plain";
    case "man": return "application/x-troff-man";
    case "manifest": return "application/x-ms-manifest";
    case "map": return "text/plain";
    case "master": return "application/xml";
    case "mda": return "application/msaccess";
    case "mdb": return "application/x-msaccess";
    case "mde": return "application/msaccess";
    case "mdp": return "application/octet-stream";
    case "me": return "application/x-troff-me";
    case "mfp": return "application/x-shockwave-flash";
    case "mht": return "message/rfc822";
    case "mhtml": return "message/rfc822";
    case "mid": return "audio/mid";
    case "midi": return "audio/mid";
    case "mix": return "application/octet-stream";
    case "mk": return "text/plain";
    case "mmf": return "application/x-smaf";
    case "mno": return "text/xml";
    case "mny": return "application/x-msmoney";
    case "mod": return "video/mpeg";
    case "mov": return "video/quicktime";
    case "movie": return "video/x-sgi-movie";
    case "mp2": return "video/mpeg";
    case "mp2v": return "video/mpeg";
    case "mp3": return "audio/mpeg";
    case "mp4": return "video/mp4";
    case "mp4v": return "video/mp4";
    case "mpa": return "video/mpeg";
    case "mpe": return "video/mpeg";
    case "mpeg": return "video/mpeg";
    case "mpf": return "application/vnd.ms-mediapackage";
    case "mpg": return "video/mpeg";
    case "mpp": return "application/vnd.ms-project";
    case "mpv2": return "video/mpeg";
    case "mqv": return "video/quicktime";
    case "ms": return "application/x-troff-ms";
    case "msi": return "application/octet-stream";
    case "mso": return "application/octet-stream";
    case "mts": return "video/vnd.dlna.mpeg-tts";
    case "mtx": return "application/xml";
    case "mvb": return "application/x-msmediaview";
    case "mvc": return "application/x-miva-compiled";
    case "mxp": return "application/x-mmxp";
    case "nc": return "application/x-netcdf";
    case "nsc": return "video/x-ms-asf";
    case "nws": return "message/rfc822";
    case "ocx": return "application/octet-stream";
    case "oda": return "application/oda";
    case "odc": return "text/x-ms-odc";
    case "odh": return "text/plain";
    case "odl": return "text/plain";
    case "odp": return "application/vnd.oasis.opendocument.presentation";
    case "ods": return "application/oleobject";
    case "odt": return "application/vnd.oasis.opendocument.text";
    case "one": return "application/onenote";
    case "onea": return "application/onenote";
    case "onepkg": return "application/onenote";
    case "onetmp": return "application/onenote";
    case "onetoc": return "application/onenote";
    case "onetoc2": return "application/onenote";
    case "orderedtest": return "application/xml";
    case "osdx": return "application/opensearchdescription+xml";
    case "p10": return "application/pkcs10";
    case "p12": return "application/x-pkcs12";
    case "p7b": return "application/x-pkcs7-certificates";
    case "p7c": return "application/pkcs7-mime";
    case "p7m": return "application/pkcs7-mime";
    case "p7r": return "application/x-pkcs7-certreqresp";
    case "p7s": return "application/pkcs7-signature";
    case "pbm": return "image/x-portable-bitmap";
    case "pcast": return "application/x-podcast";
    case "pct": return "image/pict";
    case "pcx": return "application/octet-stream";
    case "pcz": return "application/octet-stream";
    case "pdf": return "application/pdf";
    case "pfb": return "application/octet-stream";
    case "pfm": return "application/octet-stream";
    case "pfx": return "application/x-pkcs12";
    case "pgm": return "image/x-portable-graymap";
    case "pic": return "image/pict";
    case "pict": return "image/pict";
    case "pkgdef": return "text/plain";
    case "pkgundef": return "text/plain";
    case "pko": return "application/vnd.ms-pki.pko";
    case "pls": return "audio/scpls";
    case "pma": return "application/x-perfmon";
    case "pmc": return "application/x-perfmon";
    case "pml": return "application/x-perfmon";
    case "pmr": return "application/x-perfmon";
    case "pmw": return "application/x-perfmon";
    case "png": return "image/png";
    case "pnm": return "image/x-portable-anymap";
    case "pnt": return "image/x-macpaint";
    case "pntg": return "image/x-macpaint";
    case "pnz": return "image/png";
    case "pot": return "application/vnd.ms-powerpoint";
    case "potm": return "application/vnd.ms-powerpoint.template.macroenabled.12";
    case "potx": return "application/vnd.openxmlformats-officedocument.presentationml.template";
    case "ppa": return "application/vnd.ms-powerpoint";
    case "ppam": return "application/vnd.ms-powerpoint.addin.macroenabled.12";
    case "ppm": return "image/x-portable-pixmap";
    case "pps": return "application/vnd.ms-powerpoint";
    case "ppsm": return "application/vnd.ms-powerpoint.slideshow.macroenabled.12";
    case "ppsx": return "application/vnd.openxmlformats-officedocument.presentationml.slideshow";
    case "ppt": return "application/vnd.ms-powerpoint";
    case "pptm": return "application/vnd.ms-powerpoint.presentation.macroenabled.12";
    case "pptx": return "application/vnd.openxmlformats-officedocument.presentationml.presentation";
    case "prf": return "application/pics-rules";
    case "prm": return "application/octet-stream";
    case "prx": return "application/octet-stream";
    case "ps": return "application/postscript";
    case "psc1": return "application/powershell";
    case "psd": return "application/octet-stream";
    case "psess": return "application/xml";
    case "psm": return "application/octet-stream";
    case "psp": return "application/octet-stream";
    case "pub": return "application/x-mspublisher";
    case "pwz": return "application/vnd.ms-powerpoint";
    case "qht": return "text/x-html-insertion";
    case "qhtm": return "text/x-html-insertion";
    case "qt": return "video/quicktime";
    case "qti": return "image/x-quicktime";
    case "qtif": return "image/x-quicktime";
    case "qtl": return "application/x-quicktimeplayer";
    case "qxd": return "application/octet-stream";
    case "ra": return "audio/x-pn-realaudio";
    case "ram": return "audio/x-pn-realaudio";
    case "rar": return "application/octet-stream";
    case "ras": return "image/x-cmu-raster";
    case "rat": return "application/rat-file";
    case "rc": return "text/plain";
    case "rc2": return "text/plain";
    case "rct": return "text/plain";
    case "rdlc": return "application/xml";
    case "resx": return "application/xml";
    case "rf": return "image/vnd.rn-realflash";
    case "rgb": return "image/x-rgb";
    case "rgs": return "text/plain";
    case "rm": return "application/vnd.rn-realmedia";
    case "rmi": return "audio/mid";
    case "rmp": return "application/vnd.rn-rn_music_package";
    case "roff": return "application/x-troff";
    case "rpm": return "audio/x-pn-realaudio-plugin";
    case "rqy": return "text/x-ms-rqy";
    case "rtf": return "application/rtf";
    case "rtx": return "text/richtext";
    case "ruleset": return "application/xml";
    case "s": return "text/plain";
    case "safariextz": return "application/x-safari-safariextz";
    case "scd": return "application/x-msschedule";
    case "sct": return "text/scriptlet";
    case "sd2": return "audio/x-sd2";
    case "sdp": return "application/sdp";
    case "sea": return "application/octet-stream";
    case "searchconnector-ms": return "application/windows-search-connector+xml";
    case "setpay": return "application/set-payment-initiation";
    case "setreg": return "application/set-registration-initiation";
    case "settings": return "application/xml";
    case "sgimb": return "application/x-sgimb";
    case "sgml": return "text/sgml";
    case "sh": return "application/x-sh";
    case "shar": return "application/x-shar";
    case "shtml": return "text/html";
    case "sit": return "application/x-stuffit";
    case "sitemap": return "application/xml";
    case "skin": return "application/xml";
    case "sldm": return "application/vnd.ms-powerpoint.slide.macroenabled.12";
    case "sldx": return "application/vnd.openxmlformats-officedocument.presentationml.slide";
    case "slk": return "application/vnd.ms-excel";
    case "sln": return "text/plain";
    case "slupkg-ms": return "application/x-ms-license";
    case "smd": return "audio/x-smd";
    case "smi": return "application/octet-stream";
    case "smx": return "audio/x-smd";
    case "smz": return "audio/x-smd";
    case "snd": return "audio/basic";
    case "snippet": return "application/xml";
    case "snp": return "application/octet-stream";
    case "sol": return "text/plain";
    case "sor": return "text/plain";
    case "spc": return "application/x-pkcs7-certificates";
    case "spl": return "application/futuresplash";
    case "src": return "application/x-wais-source";
    case "srf": return "text/plain";
    case "ssisdeploymentmanifest": return "text/xml";
    case "ssm": return "application/streamingmedia";
    case "sst": return "application/vnd.ms-pki.certstore";
    case "stl": return "application/vnd.ms-pki.stl";
    case "sv4cpio": return "application/x-sv4cpio";
    case "sv4crc": return "application/x-sv4crc";
    case "svc": return "application/xml";
    case "swf": return "application/x-shockwave-flash";
    case "t": return "application/x-troff";
    case "tar": return "application/x-tar";
    case "tcl": return "application/x-tcl";
    case "testrunconfig": return "application/xml";
    case "testsettings": return "application/xml";
    case "tex": return "application/x-tex";
    case "texi": return "application/x-texinfo";
    case "texinfo": return "application/x-texinfo";
    case "tgz": return "application/x-compressed";
    case "thmx": return "application/vnd.ms-officetheme";
    case "thn": return "application/octet-stream";
    case "tif": return "image/tiff";
    case "tiff": return "image/tiff";
    case "tlh": return "text/plain";
    case "tli": return "text/plain";
    case "toc": return "application/octet-stream";
    case "tr": return "application/x-troff";
    case "trm": return "application/x-msterminal";
    case "trx": return "application/xml";
    case "ts": return "video/vnd.dlna.mpeg-tts";
    case "tsv": return "text/tab-separated-values";
    case "ttf": return "application/octet-stream";
    case "tts": return "video/vnd.dlna.mpeg-tts";
    case "txt": return "text/plain";
    case "u32": return "application/octet-stream";
    case "uls": return "text/iuls";
    case "user": return "text/plain";
    case "ustar": return "application/x-ustar";
    case "vb": return "text/plain";
    case "vbdproj": return "text/plain";
    case "vbk": return "video/mpeg";
    case "vbproj": return "text/plain";
    case "vbs": return "text/vbscript";
    case "vcf": return "text/x-vcard";
    case "vcproj": return "application/xml";
    case "vcs": return "text/plain";
    case "vcxproj": return "application/xml";
    case "vddproj": return "text/plain";
    case "vdp": return "text/plain";
    case "vdproj": return "text/plain";
    case "vdx": return "application/vnd.ms-visio.viewer";
    case "vml": return "text/xml";
    case "vscontent": return "application/xml";
    case "vsct": return "text/xml";
    case "vsd": return "application/vnd.visio";
    case "vsi": return "application/ms-vsi";
    case "vsix": return "application/vsix";
    case "vsixlangpack": return "text/xml";
    case "vsixmanifest": return "text/xml";
    case "vsmdi": return "application/xml";
    case "vspscc": return "text/plain";
    case "vss": return "application/vnd.visio";
    case "vsscc": return "text/plain";
    case "vssettings": return "text/xml";
    case "vssscc": return "text/plain";
    case "vst": return "application/vnd.visio";
    case "vstemplate": return "text/xml";
    case "vsto": return "application/x-ms-vsto";
    case "vsw": return "application/vnd.visio";
    case "vsx": return "application/vnd.visio";
    case "vtx": return "application/vnd.visio";
    case "wav": return "audio/wav";
    case "wave": return "audio/wav";
    case "wax": return "audio/x-ms-wax";
    case "wbk": return "application/msword";
    case "wbmp": return "image/vnd.wap.wbmp";
    case "wcm": return "application/vnd.ms-works";
    case "wdb": return "application/vnd.ms-works";
    case "wdp": return "image/vnd.ms-photo";
    case "webarchive": return "application/x-safari-webarchive";
    case "webtest": return "application/xml";
    case "wiq": return "application/xml";
    case "wiz": return "application/msword";
    case "wks": return "application/vnd.ms-works";
    case "wlmp": return "application/wlmoviemaker";
    case "wlpginstall": return "application/x-wlpg-detect";
    case "wlpginstall3": return "application/x-wlpg3-detect";
    case "wm": return "video/x-ms-wm";
    case "wma": return "audio/x-ms-wma";
    case "wmd": return "application/x-ms-wmd";
    case "wmf": return "application/x-msmetafile";
    case "wml": return "text/vnd.wap.wml";
    case "wmlc": return "application/vnd.wap.wmlc";
    case "wmls": return "text/vnd.wap.wmlscript";
    case "wmlsc": return "application/vnd.wap.wmlscriptc";
    case "wmp": return "video/x-ms-wmp";
    case "wmv": return "video/x-ms-wmv";
    case "wmx": return "video/x-ms-wmx";
    case "wmz": return "application/x-ms-wmz";
    case "wpl": return "application/vnd.ms-wpl";
    case "wps": return "application/vnd.ms-works";
    case "wri": return "application/x-mswrite";
    case "wrl": return "x-world/x-vrml";
    case "wrz": return "x-world/x-vrml";
    case "wsc": return "text/scriptlet";
    case "wsdl": return "text/xml";
    case "wvx": return "video/x-ms-wvx";
    case "x": return "application/directx";
    case "xaf": return "x-world/x-vrml";
    case "xaml": return "application/xaml+xml";
    case "xap": return "application/x-silverlight-app";
    case "xbap": return "application/x-ms-xbap";
    case "xbm": return "image/x-xbitmap";
    case "xdr": return "text/plain";
    case "xht": return "application/xhtml+xml";
    case "xhtml": return "application/xhtml+xml";
    case "xla": return "application/vnd.ms-excel";
    case "xlam": return "application/vnd.ms-excel.addin.macroenabled.12";
    case "xlc": return "application/vnd.ms-excel";
    case "xld": return "application/vnd.ms-excel";
    case "xlk": return "application/vnd.ms-excel";
    case "xll": return "application/vnd.ms-excel";
    case "xlm": return "application/vnd.ms-excel";
    case "xls": return "application/vnd.ms-excel";
    case "xlsb": return "application/vnd.ms-excel.sheet.binary.macroenabled.12";
    case "xlsm": return "application/vnd.ms-excel.sheet.macroenabled.12";
    case "xlsx": return "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
    case "xlt": return "application/vnd.ms-excel";
    case "xltm": return "application/vnd.ms-excel.template.macroenabled.12";
    case "xltx": return "application/vnd.openxmlformats-officedocument.spreadsheetml.template";
    case "xlw": return "application/vnd.ms-excel";
    case "xml": return "text/xml";
    case "xmta": return "application/xml";
    case "xof": return "x-world/x-vrml";
    case "xoml": return "text/plain";
    case "xpm": return "image/x-xpixmap";
    case "xps": return "application/vnd.ms-xpsdocument";
    case "xrm-ms": return "text/xml";
    case "xsc": return "application/xml";
    case "xsd": return "text/xml";
    case "xsf": return "text/xml";
    case "xsl": return "text/xml";
    case "xslt": return "text/xml";
    case "xsn": return "application/octet-stream";
    case "xss": return "application/xml";
    case "xtp": return "application/octet-stream";
    case "xwd": return "image/x-xwindowdump";
    case "z": return "application/x-compress";
    case "zip": return "application/x-zip-compressed";
  #endregion
    default: return "application/octet-stream";
  }
}

**使用MediaTypeNames类——>样本:MediaTypeNames. application . pdf **