我有一个网页，其中包含文件上传组件，仅将允许的文档类型上传到我的系统（仅限图像）。我不想使用正则表达式来确定文件类型并使用扩展名。
如果在C＃中有任何其他方法可以确定文件类型，请告诉我。
答案 0 :(得分：23)
我刚刚将VB.NET类转换为C＃以检测mime类型。它们将通过混合嗅探文件的前256个字节（Internet Explorer的urlmon.dll - f.e.）和一组已知类型来识别。
您还可以使用它来检查文件是否是它假装的文件（如果扩展名与类型匹配）。
// check whether or not the uploaded file is an image:
var contentType = MimeTypes.GetContentType(FileUpload1.PostedFile.FileName);
if(contentType.StartsWith("image"))
{
// do something with the image ...
}
这是班级：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.IO;
public class MimeTypes
{
private static List<string> knownTypes;
private static Dictionary<string, string> mimeTypes;
[DllImport("urlmon.dll", CharSet = CharSet.Auto)]
private static extern UInt32 FindMimeFromData(
UInt32 pBC, [MarshalAs(UnmanagedType.LPStr)]
string pwzUrl, [MarshalAs(UnmanagedType.LPArray)]
byte[] pBuffer, UInt32 cbSize, [MarshalAs(UnmanagedType.LPStr)]
string pwzMimeProposed, UInt32 dwMimeFlags, ref UInt32 ppwzMimeOut, UInt32 dwReserverd
);
public static string GetContentType(string fileName)
{
if (knownTypes == null || mimeTypes == null)
InitializeMimeTypeLists();
string contentType = "";
string extension = System.IO.Path.GetExtension(fileName).Replace(".", "").ToLower();
mimeTypes.TryGetValue(extension, out contentType);
if (string.IsNullOrEmpty(contentType) || knownTypes.Contains(contentType))
{
string headerType = ScanFileForMimeType(fileName);
if (headerType != "application/octet-stream" || string.IsNullOrEmpty(contentType))
contentType = headerType;
}
return contentType;
}
private static string ScanFileForMimeType(string fileName)
{
try
{
byte[] buffer = new byte[256];
using (FileStream fs = new FileStream(fileName, FileMode.Open))
{
int readLength = Convert.ToInt32(Math.Min(256, fs.Length));
fs.Read(buffer, 0, readLength);
}
UInt32 mimeType = default(UInt32);
FindMimeFromData(0, null, buffer, 256, null, 0, ref mimeType, 0);
IntPtr mimeTypePtr = new IntPtr(mimeType);
string mime = Marshal.PtrToStringUni(mimeTypePtr);
Marshal.FreeCoTaskMem(mimeTypePtr);
if (string.IsNullOrEmpty(mime))
mime = "application/octet-stream";
return mime;
} catch (Exception ex)
{
return "application/octet-stream";
}
}
private static void InitializeMimeTypeLists()
{
knownTypes = new string[] {
"text/plain",
"text/html",
"text/xml",
"text/richtext",
"text/scriptlet",
"audio/x-aiff",
"audio/basic",
"audio/mid",
"audio/wav",
"image/gif",
"image/jpeg",
"image/pjpeg",
"image/png",
"image/x-png",
"image/tiff",
"image/bmp",
"image/x-xbitmap",
"image/x-jg",
"image/x-emf",
"image/x-wmf",
"video/avi",
"video/mpeg",
"application/octet-stream",
"application/postscript",
"application/base64",
"application/macbinhex40",
"application/pdf",
"application/xml",
"application/atom+xml",
"application/rss+xml",
"application/x-compressed",
"application/x-zip-compressed",
"application/x-gzip-compressed",
"application/java",
"application/x-msdownload"
}.ToList();
mimeTypes = new Dictionary<string, string>();
mimeTypes.Add("3dm", "x-world/x-3dmf");
mimeTypes.Add("3dmf", "x-world/x-3dmf");
mimeTypes.Add("a", "application/octet-stream");
mimeTypes.Add("aab", "application/x-authorware-bin");
mimeTypes.Add("aam", "application/x-authorware-map");
mimeTypes.Add("aas", "application/x-authorware-seg");
mimeTypes.Add("abc", "text/vnd.abc");
mimeTypes.Add("acgi", "text/html");
mimeTypes.Add("afl", "video/animaflex");
mimeTypes.Add("ai", "application/postscript");
mimeTypes.Add("aif", "audio/aiff");
mimeTypes.Add("aifc", "audio/aiff");
mimeTypes.Add("aiff", "audio/aiff");
mimeTypes.Add("aim", "application/x-aim");
mimeTypes.Add("aip", "text/x-audiosoft-intra");
mimeTypes.Add("ani", "application/x-navi-animation");
mimeTypes.Add("aos", "application/x-nokia-9000-communicator-add-on-software");
mimeTypes.Add("aps", "application/mime");
mimeTypes.Add("arc", "application/octet-stream");
mimeTypes.Add("arj", "application/arj");
mimeTypes.Add("art", "image/x-jg");
mimeTypes.Add("asf", "video/x-ms-asf");
mimeTypes.Add("asm", "text/x-asm");
mimeTypes.Add("asp", "text/asp");
mimeTypes.Add("asx", "application/x-mplayer2");
mimeTypes.Add("au", "audio/basic");
mimeTypes.Add("avi", "video/avi");
mimeTypes.Add("avs", "video/avs-video");
mimeTypes.Add("bcpio", "application/x-bcpio");
mimeTypes.Add("bin", "application/octet-stream");
mimeTypes.Add("bm", "image/bmp");
mimeTypes.Add("bmp", "image/bmp");
mimeTypes.Add("boo", "application/book");
mimeTypes.Add("book", "application/book");
mimeTypes.Add("boz", "application/x-bzip2");
mimeTypes.Add("bsh", "application/x-bsh");
mimeTypes.Add("bz", "application/x-bzip");
mimeTypes.Add("bz2", "application/x-bzip2");
mimeTypes.Add("c", "text/plain");
mimeTypes.Add("c++", "text/plain");
mimeTypes.Add("cat", "application/vnd.ms-pki.seccat");
mimeTypes.Add("cc", "text/plain");
mimeTypes.Add("ccad", "application/clariscad");
mimeTypes.Add("cco", "application/x-cocoa");
mimeTypes.Add("cdf", "application/cdf");
mimeTypes.Add("cer", "application/pkix-cert");
mimeTypes.Add("cha", "application/x-chat");
mimeTypes.Add("chat", "application/x-chat");
mimeTypes.Add("class", "application/java");
mimeTypes.Add("com", "application/octet-stream");
mimeTypes.Add("conf", "text/plain");
mimeTypes.Add("cpio", "application/x-cpio");
mimeTypes.Add("cpp", "text/x-c");
mimeTypes.Add("cpt", "application/x-cpt");
mimeTypes.Add("crl", "application/pkcs-crl");
mimeTypes.Add("css", "text/css");
mimeTypes.Add("def", "text/plain");
mimeTypes.Add("der", "application/x-x509-ca-cert");
mimeTypes.Add("dif", "video/x-dv");
mimeTypes.Add("dir", "application/x-director");
mimeTypes.Add("dl", "video/dl");
mimeTypes.Add("doc", "application/msword");
mimeTypes.Add("dot", "application/msword");
mimeTypes.Add("dp", "application/commonground");
mimeTypes.Add("drw", "application/drafting");
mimeTypes.Add("dump", "application/octet-stream");
mimeTypes.Add("dv", "video/x-dv");
mimeTypes.Add("dvi", "application/x-dvi");
mimeTypes.Add("dwf", "drawing/x-dwf (old)");
mimeTypes.Add("dwg", "application/acad");
mimeTypes.Add("dxf", "application/dxf");
mimeTypes.Add("eps", "application/postscript");
mimeTypes.Add("es", "application/x-esrehber");
mimeTypes.Add("etx", "text/x-setext");
mimeTypes.Add("evy", "application/envoy");
mimeTypes.Add("exe", "application/octet-stream");
mimeTypes.Add("f", "text/plain");
mimeTypes.Add("f90", "text/x-fortran");
mimeTypes.Add("fdf", "application/vnd.fdf");
mimeTypes.Add("fif", "image/fif");
mimeTypes.Add("fli", "video/fli");
mimeTypes.Add("flv", "video/x-flv");
mimeTypes.Add("for", "text/x-fortran");
mimeTypes.Add("fpx", "image/vnd.fpx");
mimeTypes.Add("g", "text/plain");
mimeTypes.Add("g3", "image/g3fax");
mimeTypes.Add("gif", "image/gif");
mimeTypes.Add("gl", "video/gl");
mimeTypes.Add("gsd", "audio/x-gsm");
mimeTypes.Add("gtar", "application/x-gtar");
mimeTypes.Add("gz", "application/x-compressed");
mimeTypes.Add("h", "text/plain");
mimeTypes.Add("help", "application/x-helpfile");
mimeTypes.Add("hgl", "application/vnd.hp-hpgl");
mimeTypes.Add("hh", "text/plain");
mimeTypes.Add("hlp", "application/x-winhelp");
mimeTypes.Add("htc", "text/x-component");
mimeTypes.Add("htm", "text/html");
mimeTypes.Add("html", "text/html");
mimeTypes.Add("htmls", "text/html");
mimeTypes.Add("htt", "text/webviewhtml");
mimeTypes.Add("htx", "text/html");
mimeTypes.Add("ice", "x-conference/x-cooltalk");
mimeTypes.Add("ico", "image/x-icon");
mimeTypes.Add("idc", "text/plain");
mimeTypes.Add("ief", "image/ief");
mimeTypes.Add("iefs", "image/ief");
mimeTypes.Add("iges", "application/iges");
mimeTypes.Add("igs", "application/iges");
mimeTypes.Add("ima", "application/x-ima");
mimeTypes.Add("imap", "application/x-httpd-imap");
mimeTypes.Add("inf", "application/inf");
mimeTypes.Add("ins", "application/x-internett-signup");
mimeTypes.Add("ip", "application/x-ip2");
mimeTypes.Add("isu", "video/x-isvideo");
mimeTypes.Add("it", "audio/it");
mimeTypes.Add("iv", "application/x-inventor");
mimeTypes.Add("ivr", "i-world/i-vrml");
mimeTypes.Add("ivy", "application/x-livescreen");
mimeTypes.Add("jam", "audio/x-jam");
mimeTypes.Add("jav", "text/plain");
mimeTypes.Add("java", "text/plain");
mimeTypes.Add("jcm", "application/x-java-commerce");
mimeTypes.Add("jfif", "image/jpeg");
mimeTypes.Add("jfif-tbnl", "image/jpeg");
mimeTypes.Add("jpe", "image/jpeg");
mimeTypes.Add("jpeg", "image/jpeg");
mimeTypes.Add("jpg", "image/jpeg");
mimeTypes.Add("jps", "image/x-jps");
mimeTypes.Add("js", "application/x-javascript");
mimeTypes.Add("jut", "image/jutvision");
mimeTypes.Add("kar", "audio/midi");
mimeTypes.Add("ksh", "application/x-ksh");
mimeTypes.Add("la", "audio/nspaudio");
mimeTypes.Add("lam", "audio/x-liveaudio");
mimeTypes.Add("latex", "application/x-latex");
mimeTypes.Add("lha", "application/lha");
mimeTypes.Add("lhx", "application/octet-stream");
mimeTypes.Add("list", "text/plain");
mimeTypes.Add("lma", "audio/nspaudio");
mimeTypes.Add("log", "text/plain");
mimeTypes.Add("lsp", "application/x-lisp");
mimeTypes.Add("lst", "text/plain");
mimeTypes.Add("lsx", "text/x-la-asf");
mimeTypes.Add("ltx", "application/x-latex");
mimeTypes.Add("lzh", "application/octet-stream");
mimeTypes.Add("lzx", "application/lzx");
mimeTypes.Add("m", "text/plain");
mimeTypes.Add("m1v", "video/mpeg");
mimeTypes.Add("m2a", "audio/mpeg");
mimeTypes.Add("m2v", "video/mpeg");
mimeTypes.Add("m3u", "audio/x-mpequrl");
mimeTypes.Add("man", "application/x-troff-man");
mimeTypes.Add("map", "application/x-navimap");
mimeTypes.Add("mar", "text/plain");
mimeTypes.Add("mbd", "application/mbedlet");
mimeTypes.Add("mc$", "application/x-magic-cap-package-1.0");
mimeTypes.Add("mcd", "application/mcad");
mimeTypes.Add("mcf", "image/vasa");
mimeTypes.Add("mcp", "application/netmc");
mimeTypes.Add("me", "application/x-troff-me");
mimeTypes.Add("mht", "message/rfc822");
mimeTypes.Add("mhtml", "message/rfc822");
mimeTypes.Add("mid", "audio/midi");
mimeTypes.Add("midi", "audio/midi");
mimeTypes.Add("mif", "application/x-frame");
mimeTypes.Add("mime", "message/rfc822");
mimeTypes.Add("mjf", "audio/x-vnd.audioexplosion.mjuicemediafile");
mimeTypes.Add("mjpg", "video/x-motion-jpeg");
mimeTypes.Add("mm", "application/base64");
mimeTypes.Add("mme", "application/base64");
mimeTypes.Add("mod", "audio/mod");
mimeTypes.Add("moov", "video/quicktime");
mimeTypes.Add("mov", "video/quicktime");
mimeTypes.Add("movie", "video/x-sgi-movie");
mimeTypes.Add("mp2", "audio/mpeg");
mimeTypes.Add("mp3", "audio/mpeg3");
mimeTypes.Add("mpa", "audio/mpeg");
mimeTypes.Add("mpc", "application/x-project");
mimeTypes.Add("mpe", "video/mpeg");
mimeTypes.Add("mpeg", "video/mpeg");
mimeTypes.Add("mpg", "video/mpeg");
mimeTypes.Add("mpga", "audio/mpeg");
mimeTypes.Add("mpp", "application/vnd.ms-project");
mimeTypes.Add("mpt", "application/x-project");
mimeTypes.Add("mpv", "application/x-project");
mimeTypes.Add("mpx", "application/x-project");
mimeTypes.Add("mrc", "application/marc");
mimeTypes.Add("ms", "application/x-troff-ms");
mimeTypes.Add("mv", "video/x-sgi-movie");
mimeTypes.Add("my", "audio/make");
mimeTypes.Add("mzz", "application/x-vnd.audioexplosion.mzz");
mimeTypes.Add("nap", "image/naplps");
mimeTypes.Add("naplps", "image/naplps");
mimeTypes.Add("nc", "application/x-netcdf");
mimeTypes.Add("ncm", "application/vnd.nokia.configuration-message");
mimeTypes.Add("nif", "image/x-niff");
mimeTypes.Add("niff", "image/x-niff");
mimeTypes.Add("nix", "application/x-mix-transfer");
mimeTypes.Add("nsc", "application/x-conference");
mimeTypes.Add("nvd", "application/x-navidoc");
mimeTypes.Add("o", "application/octet-stream");
mimeTypes.Add("oda", "application/oda");
mimeTypes.Add("omc", "application/x-omc");
mimeTypes.Add("omcd", "application/x-omcdatamaker");
mimeTypes.Add("omcr", "application/x-omcregerator");
mimeTypes.Add("p", "text/x-pascal");
mimeTypes.Add("p10", "application/pkcs10");
mimeTypes.Add("p12", "application/pkcs-12");
mimeTypes.Add("p7a", "application/x-pkcs7-signature");
mimeTypes.Add("p7c", "application/pkcs7-mime");
mimeTypes.Add("pas", "text/pascal");
mimeTypes.Add("pbm", "image/x-portable-bitmap");
mimeTypes.Add("pcl", "application/vnd.hp-pcl");
mimeTypes.Add("pct", "image/x-pict");
mimeTypes.Add("pcx", "image/x-pcx");
mimeTypes.Add("pdf", "application/pdf");
mimeTypes.Add("pfunk", "audio/make");
mimeTypes.Add("pgm", "image/x-portable-graymap");
mimeTypes.Add("pic", "image/pict");
mimeTypes.Add("pict", "image/pict");
mimeTypes.Add("pkg", "application/x-newton-compatible-pkg");
mimeTypes.Add("pko", "application/vnd.ms-pki.pko");
mimeTypes.Add("pl", "text/plain");
mimeTypes.Add("plx", "application/x-pixclscript");
mimeTypes.Add("pm", "image/x-xpixmap");
mimeTypes.Add("png", "image/png");
mimeTypes.Add("pnm", "application/x-portable-anymap");
mimeTypes.Add("pot", "application/mspowerpoint");
mimeTypes.Add("pov", "model/x-pov");
mimeTypes.Add("ppa", "application/vnd.ms-powerpoint");
mimeTypes.Add("ppm", "image/x-portable-pixmap");
mimeTypes.Add("pps", "application/mspowerpoint");
mimeTypes.Add("ppt", "application/mspowerpoint");
mimeTypes.Add("ppz", "application/mspowerpoint");
mimeTypes.Add("pre", "application/x-freelance");
mimeTypes.Add("prt", "application/pro_eng");
mimeTypes.Add("ps", "application/postscript");
mimeTypes.Add("psd", "application/octet-stream");
mimeTypes.Add("pvu", "paleovu/x-pv");
mimeTypes.Add("pwz", "application/vnd.ms-powerpoint");
mimeTypes.Add("py", "text/x-script.phyton");
mimeTypes.Add("pyc", "applicaiton/x-bytecode.python");
mimeTypes.Add("qcp", "audio/vnd.qcelp");
mimeTypes.Add("qd3", "x-world/x-3dmf");
mimeTypes.Add("qd3d", "x-world/x-3dmf");
mimeTypes.Add("qif", "image/x-quicktime");
mimeTypes.Add("qt", "video/quicktime");
mimeTypes.Add("qtc", "video/x-qtc");
mimeTypes.Add("qti", "image/x-quicktime");
mimeTypes.Add("qtif", "image/x-quicktime");
mimeTypes.Add("ra", "audio/x-pn-realaudio");
mimeTypes.Add("ram", "audio/x-pn-realaudio");
mimeTypes.Add("ras", "application/x-cmu-raster");
mimeTypes.Add("rast", "image/cmu-raster");
mimeTypes.Add("rexx", "text/x-script.rexx");
mimeTypes.Add("rf", "image/vnd.rn-realflash");
mimeTypes.Add("rgb", "image/x-rgb");
mimeTypes.Add("rm", "application/vnd.rn-realmedia");
mimeTypes.Add("rmi", "audio/mid");
mimeTypes.Add("rmm", "audio/x-pn-realaudio");
mimeTypes.Add("rmp", "audio/x-pn-realaudio");
mimeTypes.Add("rng", "application/ringing-tones");
mimeTypes.Add("rnx", "application/vnd.rn-realplayer");
mimeTypes.Add("roff", "application/x-troff");
mimeTypes.Add("rp", "image/vnd.rn-realpix");
mimeTypes.Add("rpm", "audio/x-pn-realaudio-plugin");
mimeTypes.Add("rt", "text/richtext");
mimeTypes.Add("rtf", "text/richtext");
mimeTypes.Add("rtx", "application/rtf");
mimeTypes.Add("rv", "video/vnd.rn-realvideo");
mimeTypes.Add("s", "text/x-asm");
mimeTypes.Add("s3m", "audio/s3m");
mimeTypes.Add("saveme", "application/octet-stream");
mimeTypes.Add("sbk", "application/x-tbook");
mimeTypes.Add("scm", "application/x-lotusscreencam");
mimeTypes.Add("sdml", "text/plain");
mimeTypes.Add("sdp", "application/sdp");
mimeTypes.Add("sdr", "application/sounder");
mimeTypes.Add("sea", "application/sea");
mimeTypes.Add("set", "application/set");
mimeTypes.Add("sgm", "text/sgml");
mimeTypes.Add("sgml", "text/sgml");
mimeTypes.Add("sh", "application/x-bsh");
mimeTypes.Add("shtml", "text/html");
mimeTypes.Add("sid", "audio/x-psid");
mimeTypes.Add("sit", "application/x-sit");
mimeTypes.Add("skd", "application/x-koan");
mimeTypes.Add("skm", "application/x-koan");
mimeTypes.Add("skp", "application/x-koan");
mimeTypes.Add("skt", "application/x-koan");
mimeTypes.Add("sl", "application/x-seelogo");
mimeTypes.Add("smi", "application/smil");
mimeTypes.Add("smil", "application/smil");
mimeTypes.Add("snd", "audio/basic");
mimeTypes.Add("sol", "application/solids");
mimeTypes.Add("spc", "application/x-pkcs7-certificates");
mimeTypes.Add("spl", "application/futuresplash");
mimeTypes.Add("spr", "application/x-sprite");
mimeTypes.Add("sprite", "application/x-sprite");
mimeTypes.Add("src", "application/x-wais-source");
mimeTypes.Add("ssi", "text/x-server-parsed-html");
mimeTypes.Add("ssm", "application/streamingmedia");
mimeTypes.Add("sst", "application/vnd.ms-pki.certstore");
mimeTypes.Add("step", "application/step");
mimeTypes.Add("stl", "application/sla");
mimeTypes.Add("stp", "application/step");
mimeTypes.Add("sv4cpio", "application/x-sv4cpio");
mimeTypes.Add("sv4crc", "application/x-sv4crc");
mimeTypes.Add("svf", "image/vnd.dwg");
mimeTypes.Add("svr", "application/x-world");
mimeTypes.Add("swf", "application/x-shockwave-flash");
mimeTypes.Add("t", "application/x-troff");
mimeTypes.Add("talk", "text/x-speech");
mimeTypes.Add("tar", "application/x-tar");
mimeTypes.Add("tbk", "application/toolbook");
mimeTypes.Add("tcl", "application/x-tcl");
mimeTypes.Add("tcsh", "text/x-script.tcsh");
mimeTypes.Add("tex", "application/x-tex");
mimeTypes.Add("texi", "application/x-texinfo");
mimeTypes.Add("texinfo", "application/x-texinfo");
mimeTypes.Add("text", "text/plain");
mimeTypes.Add("tgz", "application/x-compressed");
mimeTypes.Add("tif", "image/tiff");
mimeTypes.Add("tr", "application/x-troff");
mimeTypes.Add("tsi", "audio/tsp-audio");
mimeTypes.Add("tsp", "audio/tsplayer");
mimeTypes.Add("tsv", "text/tab-separated-values");
mimeTypes.Add("turbot", "image/florian");
mimeTypes.Add("txt", "text/plain");
mimeTypes.Add("uil", "text/x-uil");
mimeTypes.Add("uni", "text/uri-list");
mimeTypes.Add("unis", "text/uri-list");
mimeTypes.Add("unv", "application/i-deas");
mimeTypes.Add("uri", "text/uri-list");
mimeTypes.Add("uris", "text/uri-list");
mimeTypes.Add("ustar", "application/x-ustar");
mimeTypes.Add("uu", "application/octet-stream");
mimeTypes.Add("vcd", "application/x-cdlink");
mimeTypes.Add("vcs", "text/x-vcalendar");
mimeTypes.Add("vda", "application/vda");
mimeTypes.Add("vdo", "video/vdo");
mimeTypes.Add("vew", "application/groupwise");
mimeTypes.Add("viv", "video/vivo");
mimeTypes.Add("vivo", "video/vivo");
mimeTypes.Add("vmd", "application/vocaltec-media-desc");
mimeTypes.Add("vmf", "application/vocaltec-media-file");
mimeTypes.Add("voc", "audio/voc");
mimeTypes.Add("vos", "video/vosaic");
mimeTypes.Add("vox", "audio/voxware");
mimeTypes.Add("vqe", "audio/x-twinvq-plugin");
mimeTypes.Add("vqf", "audio/x-twinvq");
mimeTypes.Add("vql", "audio/x-twinvq-plugin");
mimeTypes.Add("vrml", "application/x-vrml");
mimeTypes.Add("vrt", "x-world/x-vrt");
mimeTypes.Add("vsd", "application/x-visio");
mimeTypes.Add("vst", "application/x-visio");
mimeTypes.Add("vsw", "application/x-visio");
mimeTypes.Add("w60", "application/wordperfect6.0");
mimeTypes.Add("w61", "application/wordperfect6.1");
mimeTypes.Add("w6w", "application/msword");
mimeTypes.Add("wav", "audio/wav");
mimeTypes.Add("wb1", "application/x-qpro");
mimeTypes.Add("wbmp", "image/vnd.wap.wbmp");
mimeTypes.Add("web", "application/vnd.xara");
mimeTypes.Add("wiz", "application/msword");
mimeTypes.Add("wk1", "application/x-123");
mimeTypes.Add("wmf", "windows/metafile");
mimeTypes.Add("wml", "text/vnd.wap.wml");
mimeTypes.Add("wmlc", "application/vnd.wap.wmlc");
mimeTypes.Add("wmls", "text/vnd.wap.wmlscript");
mimeTypes.Add("wmlsc", "application/vnd.wap.wmlscriptc");
mimeTypes.Add("word", "application/msword");
mimeTypes.Add("wp", "application/wordperfect");
mimeTypes.Add("wp5", "application/wordperfect");
mimeTypes.Add("wp6", "application/wordperfect");
mimeTypes.Add("wpd", "application/wordperfect");
mimeTypes.Add("wq1", "application/x-lotus");
mimeTypes.Add("wri", "application/mswrite");
mimeTypes.Add("wrl", "application/x-world");
mimeTypes.Add("wrz", "model/vrml");
mimeTypes.Add("wsc", "text/scriplet");
mimeTypes.Add("wsrc", "application/x-wais-source");
mimeTypes.Add("wtk", "application/x-wintalk");
mimeTypes.Add("xbm", "image/x-xbitmap");
mimeTypes.Add("xdr", "video/x-amt-demorun");
mimeTypes.Add("xgz", "xgl/drawing");
mimeTypes.Add("xif", "image/vnd.xiff");
mimeTypes.Add("xl", "application/excel");
mimeTypes.Add("xla", "application/excel");
mimeTypes.Add("xlb", "application/excel");
mimeTypes.Add("xlc", "application/excel");
mimeTypes.Add("xld", "application/excel");
mimeTypes.Add("xlk", "application/excel");
mimeTypes.Add("xll", "application/excel");
mimeTypes.Add("xlm", "application/excel");
mimeTypes.Add("xls", "application/excel");
mimeTypes.Add("xlsx", "application/excel");
mimeTypes.Add("xlt", "application/excel");
mimeTypes.Add("xlv", "application/excel");
mimeTypes.Add("xlw", "application/excel");
mimeTypes.Add("xm", "audio/xm");
mimeTypes.Add("xml", "text/xml");
mimeTypes.Add("xmz", "xgl/movie");
mimeTypes.Add("xpix", "application/x-vnd.ls-xpix");
mimeTypes.Add("xpm", "image/x-xpixmap");
mimeTypes.Add("x-png", "image/png");
mimeTypes.Add("xsr", "video/x-amt-showrun");
mimeTypes.Add("xwd", "image/x-xwd");
mimeTypes.Add("xyz", "chemical/x-pdb");
mimeTypes.Add("z", "application/x-compress");
mimeTypes.Add("zip", "application/x-compressed");
mimeTypes.Add("zoo", "application/octet-stream");
mimeTypes.Add("zsh", "text/x-script.zsh");
}
}
当mime类型未知时，您必须更新此列表，并且仅知道它是application/octet-stream是不够的。检查扩展名是否为txt但mime-type是二进制数据可能就足够了，因为这意味着该文件不是它假装的文件。
除此之外，使用RegularExpressionValidator非常容易。
例如（仅限jpg图像）：
<asp:FileUpload ID="FileUpload1" runat="server" /><br />
<br />
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click"
Text="Upload File" /> <br />
<br />
<asp:Label ID="Label1" runat="server"></asp:Label>
<asp:RegularExpressionValidator
id="RegularExpressionValidator1" runat="server"
ErrorMessage="Only jpeg files are allowed!"
ValidationExpression="^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))
+(.jpg|.JPG|.jpeg|.JPEG)$"
ControlToValidate="FileUpload1"></asp:RegularExpressionValidator>
在codebehind中：
if (FileUpload1.HasFile)
{
string fileExt =
System.IO.Path.GetExtension(FileUpload1.FileName);
if (fileExt == ".jpeg" || fileExt == ".jpg")
{
//do what you want with this image
}
else
{
Label1.Text = "Only .jpeg files are allowed!";
}
}
答案 1 :(得分：3)
.NET中有一个帮助类，称为Path。 你需要的是
Path.GetExtension();
它位于System.IO名称空间中。
答案 2 :(得分：3)
这样写代码绝不是一个好主意：
\documentclass{article}
\usepackage[draft]{graphicx}
\usepackage{subcaption}
\begin{document}
\begin{figure}[h]
\centering
\begin{subfigure}{0.4\linewidth}
\label{t-SNE-a}
\includegraphics[width=\linewidth]{tsne文档嵌入展示a.pdf}
\caption{First very very long caption!}
\end{subfigure}
\begin{subfigure}{0.4\linewidth}
\label{t-SNE-b}
\includegraphics[width=\linewidth]{tsne文档嵌入展示b.pdf}
\caption{Second very very long caption!}
\end{subfigure}
\begin{subfigure}{0.4\linewidth}
\label{t-SNE-c}
\includegraphics[width=\linewidth]{tsne文档嵌入展示c.pdf}
\caption{A third caption, just a bit longer than the others.}
\end{subfigure}
\caption{General caption}
\label{t-SNE文档嵌入可视化}
\end{figure}
\end{document}
之所以这样，是因为它将为您提供文件名的扩展名。假设用户足够聪明，可以将文件名从foo.exe更改为foo.png并上传。在此代码中，将通过示例验证，这对您不利。
识别文件类型的唯一适当方法是检查它的魔术字节。根据Wikipedia的说法，该术语（“幻数”）用于文件开头的一组特定的2字节标识符，但是由于任何二进制序列都可以视为数字，因此文件格式的任何功能都可以唯一区分它可用于识别。这种方法可以更好地保证正确识别格式，并且通常可以确定有关文件的更精确信息。引用original post。
因此，一年前我遇到了同样的问题，因此我创建了library可以为您解决这种情况。它易于使用，只需几行代码，您将很安全。
答案 3 :(得分：2)
你可以使用Myrmec来识别文件类型，这个库使用文件字节头。这个库可用于nuget“Myrmec”，这是repo，myrmec也支持mime类型，你可以尝试一下。代码会是这样的：
// create a sniffer instance.
Sniffer sniffer = new Sniffer();
// populate with mata data.
sniffer.Populate(FileTypes.CommonFileTypes);
// get file head byte, may be 20 bytes enough.
byte[] fileHead = ReadFileHead();
// start match.
List<string> results = sniffer.Match(fileHead);
答案 4 :(得分：1)
HttpFileCollection hfc = Request.Files;
for (int i = 0; i < hfc.Count - 1; i++)
{
HttpPostedFile hpf = hfc(i);
if (hpf.ContentType == "image/jpeg")
{
//its a jpeg
}
}
答案 5 :(得分：1)
看到一个与此相符的例子。应该指向正确的方向。来自msdn网站。
string fileName = @"C:\mydir.old\myfile.ext";
string path = @"C:\mydir.old\";
string extension;
extension = Path.GetExtension(fileName);
Console.WriteLine("GetExtension('{0}') returns '{1}'",
fileName, extension);
extension = Path.GetExtension(path);
Console.WriteLine("GetExtension('{0}') returns '{1}'",
path, extension);
// This code produces output similar to the following:
//
// GetExtension('C:\mydir.old\myfile.ext') returns '.ext'
// GetExtension('C:\mydir.old\') returns ''
答案 6 :(得分：1)
听起来你正在寻找FindMimeFromData。 this question中有很多其他信息和代码。
答案 7 :(得分：0)
[HttpGet]
public string Get(string fileName)
{
var provider = new FileExtensionContentTypeProvider();
string contentType;
if(!provider.TryGetContentType(fileName, out contentType))
{
contentType = "application/octet-stream";
}
return contentType;
}