使用 C# 确定文件类型
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时间：2020-08-09 18:14:06 来源:igfitidea点击:
Determine the file type using C#
提问by Yagya Sharma
I have a web page that has the file upload component to upload the allowed document types only to my system (images only). I don't want to use the regular expression to determine the file type and using the extension.
我有一个包含文件上传组件的网页，可以将允许的文档类型仅上传到我的系统（仅限图像）。我不想使用正则表达式来确定文件类型和使用扩展名。
Please let me know if there is any other means of determining file types in C#.
请让我知道是否有任何其他方法可以确定 C# 中的文件类型。
回答by Robert
There is a helper class in .NET for that, called Path. What you need is
.NET 中有一个辅助类，称为 Path。你需要的是
Path.GetExtension();
It is located in the System.IO namespace.
它位于 System.IO 命名空间中。
回答by Eric Robinson
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
}
}
回答by Adam
Saw an example that was along the lines of this. Should point you in the right direction. From msdn site.
看到了一个与此类似的示例。应该为您指明正确的方向。来自 msdn 站点。
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 ''
回答by Shane Fulmer
It sounds like you're looking for FindMimeFromData. There's a lot of additional info and code in this question.
听起来您正在寻找FindMimeFromData. 这个问题中有很多额外的信息和代码。
回答by Tim Schmelter
I've just converted my VB.NETclass to C# to detect mime types. They will be identified by a mix of sniffing the first 256 Bytes of a file(urlmon.dll- f.e. used by internet explorer) and a set of known types.
我刚刚将我的VB.NET类转换为 C# 来检测 mime 类型。它们将通过嗅探文件的前 256 个字节（urlmon.dll- Internet Explorer 使用的 fe ）和一组已知类型的混合来识别。
You can also use it to check if the file is what it pretends to be(if the extension matches the type).
您还可以使用它来检查文件是否是它所伪装的（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 ...
}
Here's the class:
这是课程：
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");
}
}
You have to update this list when a mime type is unknown and it is not sufficient to know that it is application/octet-stream. It might suffice to check if an extension is txt but the mime-type is binary data, because that means that this file is not what it pretends to be.
当 mime 类型未知并且仅知道它是 是不够的时，您必须更新此列表application/octet-stream。检查扩展名是否为 txt 但 mime 类型为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那样。
Apart from that it's really easier to use a RegularExpressionValidator.
除此之外，使用RegularExpressionValidator.
For example (only jpg-images):
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>
In codebehind:
在代码隐藏中：
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!";
}
}
回答by RocketRobin
you can use Myrmec to identify the file type, this library use the file byte head. this library avaliable on nuget "Myrmec",and this is the repo, myrmec also support mime type,you can try it. the code will like this :
你可以使用Myrmec来识别文件类型，这个库使用文件字节头。这个库在nuget“Myrmec”上可用，这是repo，myrmec也支持mime类型，你可以试试。代码会像这样：
// 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);
回答by RocketRobin
It's never a good idea to write your code like that:
像这样编写代码从来都不是一个好主意：
string fileExt = System.IO.Path.GetExtension(FileUpload1.FileName);
if (fileExt == ".jpeg" || fileExt == ".jpg")
{
//do what you want with this image
}
The reason of that is because it will give you the extension from the filename. Lets assume that the user is smart enough to change the filename from foo.exe to foo.png and upload it. In this code sample validation will be passed and this is bad for you.
原因是它会给你文件名的扩展名。让我们假设用户足够聪明，可以将文件名从 foo.exe 更改为 foo.png 并上传。在此代码示例中，验证将通过，这对您不利。
The only appropriate way to identify file type is by checking it magic bytes. According to Wikipedia this term ("magic numbers") was used for a specific set of 2-byte identifiers at the beginnings of files, but since any binary sequence can be regarded as a number, any feature of a file format which uniquely distinguishes it can be used for identification. This approach offers better guarantees that the format will be identified correctly, and can often determine more precise information about the file. Reference to original post.
识别文件类型的唯一适当方法是检查它的魔术字节。根据维基百科，这个术语（“幻数”）用于文件开头的一组特定的 2 字节标识符，但由于任何二进制序列都可以被视为一个数字，因此唯一区分它的文件格式的任何特征可用于识别。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。参考原帖。
Because of that I had the same problem a year ago and I created a librarythat can help you with that scenario. It's easy to use and with few lines of code you will be safe.
因此，我在一年前遇到了同样的问题，我创建了一个可以帮助您解决该场景的库。它易于使用，只需几行代码即可确保安全。
