从文件名扩展名获取MIME类型

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

2016-10-30 16:09:45

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。

2013-07-11 07:35:38

您可以使用Apache的httpd提供的表。将其映射到函数、字典、列表等应该是很简单的。

另外，正如这里所看到的，extension->mime类型不一定是函数。每个文件扩展名可能有多种常见的MIME类型，所以你应该看看你的应用程序的需求，看看你为什么关心MIME类型，你想用它们“做什么”等等。您可以使用文件扩展名来确定相同的行为吗?您是否也需要读取文件的前几个字节来确定其MIME类型?

2009-06-22 22:52:15

我更新了一些剧本。以防有人需要

2022-05-03 06:30:15

您不应该信任来自客户端的文件扩展名。总是检查文件的神奇数字。

使用filetpe讯问器与ASP。NET核心:

public static class FileTypeChecker
{
    private static List<string> validVideoMimeTypes = new List<string> { "video/mp4", "video/quicktime" };
    private static List<string> validImageMimeTypes = new List<string> { "image/png", "image/jpeg" };

    public static bool IsValidVideo(IFormFile file)
    {
        return validVideoMimeTypes.Contains(GetFileMimeType(file));
    }

    public static bool IsValidImage(IFormFile file)
    {
        return validImageMimeTypes.Contains(GetFileMimeType(file));
    }

    private static string GetFileMimeType(IFormFile file)
    {
        // You should have checked for null and file length before reaching here

        IFileTypeInterrogator interrogator = new FileTypeInterrogator.FileTypeInterrogator();

        byte[] fileBytes;
        using (var stream = new MemoryStream())
        {
            file.CopyTo(stream);
            fileBytes = stream.ToArray();
        }

        FileTypeInfo fileTypeInfo = interrogator.DetectType(fileBytes);
        return fileTypeInfo.MimeType.ToLower();
    }
}

在你的控制器或服务内部:

public IActionResult UploadVideo([FromForm] UploadVideoVM model)
{
    if (model.File.Length < minimumLength || model.File.Length > maximumLength)
    {
        // BadRequest => Size
    }
    else if (!FileTypeChecker.IsValidVideo(model.File))
    {
        // BadRequest => Type
    }
    else
    {
        // All good
    }

    return Ok();
}

要获得文件扩展名的MIME类型，请参考此文件。

2020-08-24 09:38:24

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;

2009-06-22 22:51:33

从文件名扩展名获取MIME类型

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