为了使这篇文章更全面，对于。net核心开发人员有FileExtensionContentTypeProvider类，它涵盖了官方的MIME内容类型。

它在幕后工作——根据文件扩展名在Http响应头中设置ContentType。

如果您需要特殊的MIME类型，请参阅自定义MIME类型的示例:

public void Configure(IApplicationBuilder app)
{
    // Set up custom content types -associating file extension to MIME type
    var provider = new FileExtensionContentTypeProvider();
    // Add new mappings
    provider.Mappings[".myapp"] = "application/x-msdownload";
    provider.Mappings[".htm3"] = "text/html";
    provider.Mappings[".image"] = "image/png";
    // Replace an existing mapping
    provider.Mappings[".rtf"] = "application/x-msdownload";
    // Remove MP4 videos.
    provider.Mappings.Remove(".mp4");

    app.UseStaticFiles(new StaticFileOptions()
    {
        FileProvider = new PhysicalFileProvider(
            Path.Combine(Directory.GetCurrentDirectory(), @"wwwroot", "images")),
        RequestPath = new PathString("/MyImages"),
        ContentTypeProvider = provider
    });

    app.UseDirectoryBrowser(new DirectoryBrowserOptions()
    {
        FileProvider = new PhysicalFileProvider(
            Path.Combine(Directory.GetCurrentDirectory(), @"wwwroot", "images")),
        RequestPath = new PathString("/MyImages")
    });
}

这个helper类返回任何文件名的mime类型(内容类型)、描述和图标:

using Microsoft.Win32;
using System;
using System.Drawing;
using System.IO;
using System.Runtime.InteropServices;

public static class Helper
{
    [DllImport("shell32.dll", CharSet = CharSet.Auto)]
    private static extern int ExtractIconEx(string lpszFile, int nIconIndex, IntPtr[] phIconLarge, IntPtr[] phIconSmall, int nIcons);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern int DestroyIcon(IntPtr hIcon);

    public static string GetFileContentType(string fileName)
    {
        if (fileName == null)
        {
            throw new ArgumentNullException("fileName");
        }

        RegistryKey registryKey = null;
        try
        {
            FileInfo fileInfo = new FileInfo(fileName);

            if (string.IsNullOrEmpty(fileInfo.Extension))
            {
                return string.Empty;
            }

            string extension = fileInfo.Extension.ToLowerInvariant();

            registryKey = Registry.ClassesRoot.OpenSubKey(extension);
            if (registryKey == null)
            {
                return string.Empty;
            }

            object contentTypeObject = registryKey.GetValue("Content Type");
            if (!(contentTypeObject is string))
            {
                return string.Empty;
            }

            string contentType = (string)contentTypeObject;

            return contentType;
        }
        catch (Exception)
        {
            return null;
        }
        finally
        {
            if (registryKey != null)
            {
                registryKey.Close();
            }
        }
    }

    public static string GetFileDescription(string fileName)
    {
        if (fileName == null)
        {
            throw new ArgumentNullException("fileName");
        }

        RegistryKey registryKey1 = null;
        RegistryKey registryKey2 = null;
        try
        {
            FileInfo fileInfo = new FileInfo(fileName);

            if (string.IsNullOrEmpty(fileInfo.Extension))
            {
                return string.Empty;
            }

            string extension = fileInfo.Extension.ToLowerInvariant();

            registryKey1 = Registry.ClassesRoot.OpenSubKey(extension);
            if (registryKey1 == null)
            {
                return string.Empty;
            }

            object extensionDefaultObject = registryKey1.GetValue(null);
            if (!(extensionDefaultObject is string))
            {
                return string.Empty;
            }

            string extensionDefaultValue = (string)extensionDefaultObject;

            registryKey2 = Registry.ClassesRoot.OpenSubKey(extensionDefaultValue);
            if (registryKey2 == null)
            {
                return string.Empty;
            }

            object fileDescriptionObject = registryKey2.GetValue(null);
            if (!(fileDescriptionObject is string))
            {
                return string.Empty;
            }

            string fileDescription = (string)fileDescriptionObject;
            return fileDescription;
        }
        catch (Exception)
        {
            return null;
        }
        finally
        {
            if (registryKey2 != null)
            {
                registryKey2.Close();
            }

            if (registryKey1 != null)
            {
                registryKey1.Close();
            }
        }
    }

    public static void GetFileIcons(string fileName, out Icon smallIcon, out Icon largeIcon)
    {
        if (fileName == null)
        {
            throw new ArgumentNullException("fileName");
        }

        smallIcon = null;
        largeIcon = null;

        RegistryKey registryKey1 = null;
        RegistryKey registryKey2 = null;
        try
        {
            FileInfo fileInfo = new FileInfo(fileName);

            if (string.IsNullOrEmpty(fileInfo.Extension))
            {
                return;
            }

            string extension = fileInfo.Extension.ToLowerInvariant();

            registryKey1 = Registry.ClassesRoot.OpenSubKey(extension);
            if (registryKey1 == null)
            {
                return;
            }

            object extensionDefaultObject = registryKey1.GetValue(null);
            if (!(extensionDefaultObject is string))
            {
                return;
            }

            string defaultIconKeyName = string.Format("{0}\\DefaultIcon", extensionDefaultObject);

            registryKey2 = Registry.ClassesRoot.OpenSubKey(defaultIconKeyName);
            if (registryKey2 == null)
            {
                return;
            }

            object defaultIconPathObject = registryKey2.GetValue(null);
            if (!(defaultIconPathObject is string))
            {
                return;
            }

            string defaultIconPath = (string)defaultIconPathObject;
            if (string.IsNullOrWhiteSpace(defaultIconPath))
            {
                return;
            }

            string iconfileName = null;
            int iconIndex = 0;

            int commaIndex = defaultIconPath.IndexOf(",");
            if (commaIndex > 0)
            {
                iconfileName = defaultIconPath.Substring(0, commaIndex);
                string iconIndexString = defaultIconPath.Substring(commaIndex + 1);

                if (!int.TryParse(iconIndexString, out iconIndex))
                {
                    iconIndex = 0;
                }
            }
            else
            {
                iconfileName = defaultIconPath;
                iconIndex = 0;
            }

            IntPtr[] phiconSmall = new IntPtr[1] { IntPtr.Zero };
            IntPtr[] phiconLarge = new IntPtr[1] { IntPtr.Zero };

            int readIconCount = ExtractIconEx(iconfileName, iconIndex, phiconLarge, phiconSmall, 1);

            if (readIconCount < 0)
            {
                return;
            }

            if (phiconSmall[0] != IntPtr.Zero)
            {
                smallIcon = (Icon)Icon.FromHandle(phiconSmall[0]).Clone();
                DestroyIcon(phiconSmall[0]);
            }

            if (phiconLarge[0] != IntPtr.Zero)
            {
                largeIcon = (Icon)Icon.FromHandle(phiconLarge[0]).Clone();
                DestroyIcon(phiconLarge[0]);
            }

            return;
        }
        finally
        {
            if (registryKey2 != null)
            {
                registryKey2.Close();
            }

            if (registryKey1 != null)
            {
                registryKey1.Close();
            }
        }
    }
}

用法:

string fileName = "NotExists.txt";
string contentType = Helper.GetFileContentType(fileName); // "text/plain"
string description = Helper.GetFileDescription(fileName); // "Text Document"
Icon smallIcon, largeIcon;
Helper.GetFileIcons(fileName, out smallIcon, out largeIcon); // 16x16, 32x32 icons

受到塞缪尔回答的启发，我写了一个改进版本:

当扩展名是大写时也适用。 以文件名为输入，优雅地处理没有扩展名的文件。 不要在键中包含“。”。 列表，为此我编写了一个小型转换脚本。

最终的源代码超过30K个字符，所以我不能张贴在这里，在Github上检查它。

IANA媒体类型

我希望微软能把他们的行业标准统一起来!对于其他人，有兴趣的人:

离散的类型

application: https://www.iana.org/assignments/media-types/media-types.xhtml#application audio: https://www.iana.org/assignments/media-types/media-types.xhtml#audio example: https://www.iana.org/assignments/media-types/media-types.xhtml#examples font: https://www.iana.org/assignments/media-types/media-types.xhtml#font image: https://www.iana.org/assignments/media-types/media-types.xhtml#image model: https://www.iana.org/assignments/media-types/media-types.xhtml#model text: https://www.iana.org/assignments/media-types/media-types.xhtml#text video: https://www.iana.org/assignments/media-types/media-types.xhtml#video

多部分类型

信息:https://www.iana.org/assignments/media-types/media-types.xhtml消息 多部分:https://www.iana.org/assignments/media-types/media-types.xhtml #多部分

我想推荐一个阅读:MIME类型(IANA媒体类型)的Mozilla页面感兴趣的人!它的信息量很大!

在代码方面，上面的每个链接都有一个.csv文件下载:https://www.iana.org/assignments/media-types/application.csv

正如这里已经指出的，可以使用Dictionary或ConcurrentDictionary下载并使用Key - Value对填充Dictionary。

如果有人能在linux上使用libmagic类似的功能，那就更好了，因为我认为这是一种比依赖文件扩展名更好的检测文件类型的方法。

例如，如果我将一个文件从myppicture .jpg重命名为myppicture .txt 在linux上，它仍然会被报告为一张图片 但是在这里使用这种方法，它将被报告为文本文件。

目光Tomas

. net框架提供了获取mime类型的内置方法。不需要编写自定义代码。

string mimeType = System.Web.MimeMapping.GetMimeMapping(fileName);