我正在寻找一种简单的方法来获得mime类型，其中文件扩展名是不正确的或没有给出，类似于这个问题只有在. net。
当前回答
如果你想要托管你的ASP. mimetype，来自Nuget的guessmimetype将是最终的解决方案。NET解决方案在非windows环境。
文件扩展名映射非常不安全。如果攻击者上传无效的扩展名，映射字典将允许可执行文件在.jpg文件中分发。 因此，始终使用内容嗅探库来了解真正的内容类型。
public static string MimeTypeFrom(byte[] dataBytes, string fileName)
{
var contentType = HeyRed.Mime.MimeGuesser.GuessMimeType(dataBytes);
if (string.IsNullOrEmpty(contentType))
{
return HeyRed.Mime.MimeTypesMap.GetMimeType(fileName);
}
return contentType;
其他回答
在Urlmon.dll中，有一个名为FindMimeFromData的函数。
来自文档
MIME类型检测或“数据嗅探”是指从二进制数据中确定适当的MIME类型的过程。最终结果取决于服务器提供的MIME类型头、文件扩展名和/或数据本身的组合。通常，只有前256字节的数据是重要的。
因此，从文件中读取第一个(最多)256字节，并将其传递给FindMimeFromData。
你好，我已经改编了Winista。MimeDetect项目到。net core/framework，回退到urlmon.dll，自由使用它:nuget包。
//init
var mimeTypes = new MimeTypes();
//usage by filepath
var mimeType1 = mimeTypes.GetMimeTypeFromFile(filePath);
最后我确实使用了urlmon.dll。我本以为有更简单的方法，但这招管用。我包含了代码来帮助其他人，并允许我在需要时再次找到它。
using System.Runtime.InteropServices;
...
[DllImport(@"urlmon.dll", CharSet = CharSet.Auto)]
private extern static System.UInt32 FindMimeFromData(
System.UInt32 pBC,
[MarshalAs(UnmanagedType.LPStr)] System.String pwzUrl,
[MarshalAs(UnmanagedType.LPArray)] byte[] pBuffer,
System.UInt32 cbSize,
[MarshalAs(UnmanagedType.LPStr)] System.String pwzMimeProposed,
System.UInt32 dwMimeFlags,
out System.UInt32 ppwzMimeOut,
System.UInt32 dwReserverd
);
public static string getMimeFromFile(string filename)
{
if (!File.Exists(filename))
throw new FileNotFoundException(filename + " not found");
byte[] buffer = new byte[256];
using (FileStream fs = new FileStream(filename, FileMode.Open))
{
if (fs.Length >= 256)
fs.Read(buffer, 0, 256);
else
fs.Read(buffer, 0, (int)fs.Length);
}
try
{
System.UInt32 mimetype;
FindMimeFromData(0, null, buffer, 256, null, 0, out mimetype, 0);
System.IntPtr mimeTypePtr = new IntPtr(mimetype);
string mime = Marshal.PtrToStringUni(mimeTypePtr);
Marshal.FreeCoTaskMem(mimeTypePtr);
return mime;
}
catch (Exception e)
{
return "unknown/unknown";
}
}
当使用Windows Azure Web角色或在有限信任中运行应用程序的任何其他主机时，不要忘记您将不允许访问注册表或非托管代码。混合方法——try-catch-for registry和内存字典的组合看起来是一个很好的解决方案，它什么都有。
我用下面的代码来做:
public class DefaultMimeResolver : IMimeResolver
{
private readonly IFileRepository _fileRepository;
public DefaultMimeResolver(IFileRepository fileRepository)
{
_fileRepository = fileRepository;
}
[DllImport(@"urlmon.dll", CharSet = CharSet.Auto)]
private static extern System.UInt32 FindMimeFromData(
System.UInt32 pBC, [MarshalAs(UnmanagedType.LPStr)] System.String pwzUrl,
[MarshalAs(UnmanagedType.LPArray)] byte[] pBuffer,
System.UInt32 cbSize,
[MarshalAs(UnmanagedType.LPStr)] System.String pwzMimeProposed,
System.UInt32 dwMimeFlags,
out System.UInt32 ppwzMimeOut,
System.UInt32 dwReserverd);
public string GetMimeTypeFromFileExtension(string fileExtension)
{
if (string.IsNullOrEmpty(fileExtension))
{
throw new ArgumentNullException("fileExtension");
}
string mimeType = GetMimeTypeFromList(fileExtension);
if (String.IsNullOrEmpty(mimeType))
{
mimeType = GetMimeTypeFromRegistry(fileExtension);
}
return mimeType;
}
public string GetMimeTypeFromFile(string filePath)
{
if (string.IsNullOrEmpty(filePath))
{
throw new ArgumentNullException("filePath");
}
if (!File.Exists(filePath))
{
throw new FileNotFoundException("File not found : ", filePath);
}
string mimeType = GetMimeTypeFromList(Path.GetExtension(filePath).ToLower());
if (String.IsNullOrEmpty(mimeType))
{
mimeType = GetMimeTypeFromRegistry(Path.GetExtension(filePath).ToLower());
if (String.IsNullOrEmpty(mimeType))
{
mimeType = GetMimeTypeFromFileInternal(filePath);
}
}
return mimeType;
}
private string GetMimeTypeFromList(string fileExtension)
{
string mimeType = null;
if (fileExtension.StartsWith("."))
{
fileExtension = fileExtension.TrimStart('.');
}
if (!String.IsNullOrEmpty(fileExtension) && _mimeTypes.ContainsKey(fileExtension))
{
mimeType = _mimeTypes[fileExtension];
}
return mimeType;
}
private string GetMimeTypeFromRegistry(string fileExtension)
{
string mimeType = null;
try
{
RegistryKey key = Registry.ClassesRoot.OpenSubKey(fileExtension);
if (key != null && key.GetValue("Content Type") != null)
{
mimeType = key.GetValue("Content Type").ToString();
}
}
catch (Exception)
{
// Empty. When this code is running in limited mode accessing registry is not allowed.
}
return mimeType;
}
private string GetMimeTypeFromFileInternal(string filePath)
{
string mimeType = null;
if (!File.Exists(filePath))
{
return null;
}
byte[] byteBuffer = new byte[256];
using (FileStream fileStream = _fileRepository.Get(filePath))
{
if (fileStream.Length >= 256)
{
fileStream.Read(byteBuffer, 0, 256);
}
else
{
fileStream.Read(byteBuffer, 0, (int)fileStream.Length);
}
}
try
{
UInt32 MimeTypeNum;
FindMimeFromData(0, null, byteBuffer, 256, null, 0, out MimeTypeNum, 0);
IntPtr mimeTypePtr = new IntPtr(MimeTypeNum);
string mimeTypeFromFile = Marshal.PtrToStringUni(mimeTypePtr);
Marshal.FreeCoTaskMem(mimeTypePtr);
if (!String.IsNullOrEmpty(mimeTypeFromFile) && mimeTypeFromFile != "text/plain" && mimeTypeFromFile != "application/octet-stream")
{
mimeType = mimeTypeFromFile;
}
}
catch
{
// Empty.
}
return mimeType;
}
private readonly Dictionary<string, string> _mimeTypes = new Dictionary<string, string>
{
{"ai", "application/postscript"},
{"aif", "audio/x-aiff"},
{"aifc", "audio/x-aiff"},
{"aiff", "audio/x-aiff"},
{"asc", "text/plain"},
{"atom", "application/atom+xml"},
{"au", "audio/basic"},
{"avi", "video/x-msvideo"},
{"bcpio", "application/x-bcpio"},
{"bin", "application/octet-stream"},
{"bmp", "image/bmp"},
{"cdf", "application/x-netcdf"},
{"cgm", "image/cgm"},
{"class", "application/octet-stream"},
{"cpio", "application/x-cpio"},
{"cpt", "application/mac-compactpro"},
{"csh", "application/x-csh"},
{"css", "text/css"},
{"dcr", "application/x-director"},
{"dif", "video/x-dv"},
{"dir", "application/x-director"},
{"djv", "image/vnd.djvu"},
{"djvu", "image/vnd.djvu"},
{"dll", "application/octet-stream"},
{"dmg", "application/octet-stream"},
{"dms", "application/octet-stream"},
{"doc", "application/msword"},
{"docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document"},
{"dotx", "application/vnd.openxmlformats-officedocument.wordprocessingml.template"},
{"docm", "application/vnd.ms-word.document.macroEnabled.12"},
{"dotm", "application/vnd.ms-word.template.macroEnabled.12"},
{"dtd", "application/xml-dtd"},
{"dv", "video/x-dv"},
{"dvi", "application/x-dvi"},
{"dxr", "application/x-director"},
{"eps", "application/postscript"},
{"etx", "text/x-setext"},
{"exe", "application/octet-stream"},
{"ez", "application/andrew-inset"},
{"gif", "image/gif"},
{"gram", "application/srgs"},
{"grxml", "application/srgs+xml"},
{"gtar", "application/x-gtar"},
{"hdf", "application/x-hdf"},
{"hqx", "application/mac-binhex40"},
{"htc", "text/x-component"},
{"htm", "text/html"},
{"html", "text/html"},
{"ice", "x-conference/x-cooltalk"},
{"ico", "image/x-icon"},
{"ics", "text/calendar"},
{"ief", "image/ief"},
{"ifb", "text/calendar"},
{"iges", "model/iges"},
{"igs", "model/iges"},
{"jnlp", "application/x-java-jnlp-file"},
{"jp2", "image/jp2"},
{"jpe", "image/jpeg"},
{"jpeg", "image/jpeg"},
{"jpg", "image/jpeg"},
{"js", "application/x-javascript"},
{"kar", "audio/midi"},
{"latex", "application/x-latex"},
{"lha", "application/octet-stream"},
{"lzh", "application/octet-stream"},
{"m3u", "audio/x-mpegurl"},
{"m4a", "audio/mp4a-latm"},
{"m4b", "audio/mp4a-latm"},
{"m4p", "audio/mp4a-latm"},
{"m4u", "video/vnd.mpegurl"},
{"m4v", "video/x-m4v"},
{"mac", "image/x-macpaint"},
{"man", "application/x-troff-man"},
{"mathml", "application/mathml+xml"},
{"me", "application/x-troff-me"},
{"mesh", "model/mesh"},
{"mid", "audio/midi"},
{"midi", "audio/midi"},
{"mif", "application/vnd.mif"},
{"mov", "video/quicktime"},
{"movie", "video/x-sgi-movie"},
{"mp2", "audio/mpeg"},
{"mp3", "audio/mpeg"},
{"mp4", "video/mp4"},
{"mpe", "video/mpeg"},
{"mpeg", "video/mpeg"},
{"mpg", "video/mpeg"},
{"mpga", "audio/mpeg"},
{"ms", "application/x-troff-ms"},
{"msh", "model/mesh"},
{"mxu", "video/vnd.mpegurl"},
{"nc", "application/x-netcdf"},
{"oda", "application/oda"},
{"ogg", "application/ogg"},
{"pbm", "image/x-portable-bitmap"},
{"pct", "image/pict"},
{"pdb", "chemical/x-pdb"},
{"pdf", "application/pdf"},
{"pgm", "image/x-portable-graymap"},
{"pgn", "application/x-chess-pgn"},
{"pic", "image/pict"},
{"pict", "image/pict"},
{"png", "image/png"},
{"pnm", "image/x-portable-anymap"},
{"pnt", "image/x-macpaint"},
{"pntg", "image/x-macpaint"},
{"ppm", "image/x-portable-pixmap"},
{"ppt", "application/vnd.ms-powerpoint"},
{"pptx", "application/vnd.openxmlformats-officedocument.presentationml.presentation"},
{"potx", "application/vnd.openxmlformats-officedocument.presentationml.template"},
{"ppsx", "application/vnd.openxmlformats-officedocument.presentationml.slideshow"},
{"ppam", "application/vnd.ms-powerpoint.addin.macroEnabled.12"},
{"pptm", "application/vnd.ms-powerpoint.presentation.macroEnabled.12"},
{"potm", "application/vnd.ms-powerpoint.template.macroEnabled.12"},
{"ppsm", "application/vnd.ms-powerpoint.slideshow.macroEnabled.12"},
{"ps", "application/postscript"},
{"qt", "video/quicktime"},
{"qti", "image/x-quicktime"},
{"qtif", "image/x-quicktime"},
{"ra", "audio/x-pn-realaudio"},
{"ram", "audio/x-pn-realaudio"},
{"ras", "image/x-cmu-raster"},
{"rdf", "application/rdf+xml"},
{"rgb", "image/x-rgb"},
{"rm", "application/vnd.rn-realmedia"},
{"roff", "application/x-troff"},
{"rtf", "text/rtf"},
{"rtx", "text/richtext"},
{"sgm", "text/sgml"},
{"sgml", "text/sgml"},
{"sh", "application/x-sh"},
{"shar", "application/x-shar"},
{"silo", "model/mesh"},
{"sit", "application/x-stuffit"},
{"skd", "application/x-koan"},
{"skm", "application/x-koan"},
{"skp", "application/x-koan"},
{"skt", "application/x-koan"},
{"smi", "application/smil"},
{"smil", "application/smil"},
{"snd", "audio/basic"},
{"so", "application/octet-stream"},
{"spl", "application/x-futuresplash"},
{"src", "application/x-wais-source"},
{"sv4cpio", "application/x-sv4cpio"},
{"sv4crc", "application/x-sv4crc"},
{"svg", "image/svg+xml"},
{"swf", "application/x-shockwave-flash"},
{"t", "application/x-troff"},
{"tar", "application/x-tar"},
{"tcl", "application/x-tcl"},
{"tex", "application/x-tex"},
{"texi", "application/x-texinfo"},
{"texinfo", "application/x-texinfo"},
{"tif", "image/tiff"},
{"tiff", "image/tiff"},
{"tr", "application/x-troff"},
{"tsv", "text/tab-separated-values"},
{"txt", "text/plain"},
{"ustar", "application/x-ustar"},
{"vcd", "application/x-cdlink"},
{"vrml", "model/vrml"},
{"vxml", "application/voicexml+xml"},
{"wav", "audio/x-wav"},
{"wbmp", "image/vnd.wap.wbmp"},
{"wbmxl", "application/vnd.wap.wbxml"},
{"wml", "text/vnd.wap.wml"},
{"wmlc", "application/vnd.wap.wmlc"},
{"wmls", "text/vnd.wap.wmlscript"},
{"wmlsc", "application/vnd.wap.wmlscriptc"},
{"wrl", "model/vrml"},
{"xbm", "image/x-xbitmap"},
{"xht", "application/xhtml+xml"},
{"xhtml", "application/xhtml+xml"},
{"xls", "application/vnd.ms-excel"},
{"xml", "application/xml"},
{"xpm", "image/x-xpixmap"},
{"xsl", "application/xml"},
{"xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"},
{"xltx", "application/vnd.openxmlformats-officedocument.spreadsheetml.template"},
{"xlsm", "application/vnd.ms-excel.sheet.macroEnabled.12"},
{"xltm", "application/vnd.ms-excel.template.macroEnabled.12"},
{"xlam", "application/vnd.ms-excel.addin.macroEnabled.12"},
{"xlsb", "application/vnd.ms-excel.sheet.binary.macroEnabled.12"},
{"xslt", "application/xslt+xml"},
{"xul", "application/vnd.mozilla.xul+xml"},
{"xwd", "image/x-xwindowdump"},
{"xyz", "chemical/x-xyz"},
{"zip", "application/zip"}
};
}
您也可以查看注册表。
using System.IO;
using Microsoft.Win32;
string GetMimeType(FileInfo fileInfo)
{
string mimeType = "application/unknown";
RegistryKey regKey = Registry.ClassesRoot.OpenSubKey(
fileInfo.Extension.ToLower()
);
if(regKey != null)
{
object contentType = regKey.GetValue("Content Type");
if(contentType != null)
mimeType = contentType.ToString();
}
return mimeType;
}
无论如何，您都必须利用mime数据库——无论它们是从扩展还是魔术数字映射的，都有点微不足道——windows注册表就是这样一个地方。 对于独立于平台的解决方案，必须将此DB与代码一起发布(或作为独立的库)。
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