我对这些mimetypes的理解，使用apache列表，下面的脚本将为您提供一个包含所有mimetypes的字典。

var mimeTypeListUrl = "http://svn.apache.org/repos/asf/httpd/httpd/trunk/docs/conf/mime.types";
var webClient = new WebClient();
var rawData = webClient.DownloadString(mimeTypeListUrl).Split(new[] { Environment.NewLine, "\n" }, StringSplitOptions.RemoveEmptyEntries);

var extensionToMimeType = new Dictionary<string, string>();
var mimeTypeToExtension = new Dictionary<string, string[]>();

foreach (var row in rawData)
{
    if (row.StartsWith("#")) continue;

    var rowData = row.Split(new[] { "\t" }, StringSplitOptions.RemoveEmptyEntries);
    if (rowData.Length != 2) continue;

    var extensions = rowData[1].Split(new[] { " " }, StringSplitOptions.RemoveEmptyEntries);
    if (!mimeTypeToExtension.ContainsKey(rowData[0]))
    {
        mimeTypeToExtension.Add(rowData[0], extensions);
    }

    foreach (var extension in extensions)
    {
        if (!extensionToMimeType.ContainsKey(extension))
        {
            extensionToMimeType.Add(extension, rowData[0]);
        }
    }

}

Bryan Denny上面的帖子不适合我，因为不是所有的扩展在注册表中都有一个“内容类型”子键。我不得不调整代码如下:

private string GetMimeType(string sFileName)
{
  // Get file extension and if it is empty, return unknown
  string sExt = Path.GetExtension(sFileName);
  if (string.IsNullOrEmpty(sExt)) return "Unknown file type";

  // Default type is "EXT File"
  string mimeType = string.Format("{0} File", sExt.ToUpper().Replace(".", ""));

  // Open the registry key for the extension under HKEY_CLASSES_ROOT and return default if it doesn't exist
  Microsoft.Win32.RegistryKey regKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(sExt);
  if (regKey == null) return mimeType;

  // Get the "(Default)" value and re-open the key for that value
  string sSubType = regKey.GetValue("").ToString();
  regKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(sSubType);

  // If it exists, get the "(Default)" value of the new key
  if (regKey?.GetValue("") != null) mimeType = regKey.GetValue("").ToString();

  // Return the value
  return mimeType;
}

现在它可以为我所有注册的文件类型和未注册的或通用的文件类型(如JPG等)。

. 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);

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。

如果你不想增加额外的依赖关系，并且仍然想要版本独立的请求，你可以把这个关于如何在不同的。net版本中获得MIME-Type的答案与这个关于多个。net框架版本的条件构建的答案混合在一起。

我做的第一件事是编辑我的项目文件。在最后一个构建定义之后，我添加了第二个答案中所述的属性组:

<PropertyGroup>
    <DefineConstants Condition=" !$(DefineConstants.Contains(';NET')) ">$(DefineConstants);$(TargetFrameworkVersion.Replace("v", "NET").Replace(".", ""))</DefineConstants>
    <DefineConstants Condition=" $(DefineConstants.Contains(';NET')) ">$(DefineConstants.Remove($(DefineConstants.LastIndexOf(";NET"))));$(TargetFrameworkVersion.Replace("v", "NET").Replace(".", ""))</DefineConstants>
</PropertyGroup>

现在我为MimeExtensionHelper提供了一个与第一个答案不同的实现，并为所有来自。net 4.5或更高版本的客户端提供了一个额外的实现，只需调用System.Web.MimeMapping.GetMimeMapping:

#if (NET10 || NET11 || NET20 || NET30 || NET35)
public static class MimeExtensionHelper
{
    static object locker = new object();
    static MethodInfo getMimeMappingMethodInfo;

    static MimeExtensionHelper()
    {
        Type mimeMappingType = Assembly.GetAssembly(typeof(HttpRuntime)).GetType("System.Web.MimeMapping");

        if (mimeMappingType == null)
            throw new SystemException("Couldnt find MimeMapping type");

        ConstructorInfo constructorInfo = mimeMappingType.GetConstructor(BindingFlags.NonPublic | BindingFlags.Instance, null, Type.EmptyTypes, null);

        if (constructorInfo == null)
            throw new SystemException("Couldnt find default constructor for MimeMapping");

        mimeMapping = constructorInfo.Invoke(null);

        if (mimeMapping == null)
            throw new SystemException("Couldnt find MimeMapping");

        getMimeMappingMethodInfo = mimeMappingType.GetMethod("GetMimeMapping", BindingFlags.Static | BindingFlags.NonPublic);

        if (getMimeMappingMethodInfo == null)
            throw new SystemException("Couldnt find GetMimeMapping method");

        if (getMimeMappingMethodInfo.ReturnType != typeof(string))
            throw new SystemException("GetMimeMapping method has invalid return type");

        if (getMimeMappingMethodInfo.GetParameters().Length != 1 && getMimeMappingMethodInfo.GetParameters()[0].ParameterType != typeof(string))
            throw new SystemException("GetMimeMapping method has invalid parameters");
    }

    public static string GetMimeType(string fileName)
    {
        lock (locker)
        {
            return (string)getMimeMappingMethodInfo.Invoke(null, new object[] { fileName });
        }
    }
}
#elif NET40
public static class MimeExtensionHelper
{
    static object locker = new object();
    static MethodInfo getMimeMappingMethodInfo;

    static MimeExtensionHelper()
    {
        Type mimeMappingType = Assembly.GetAssembly(typeof(HttpRuntime)).GetType("System.Web.MimeMapping");

        if (mimeMappingType == null)
            throw new SystemException("Couldnt find MimeMapping type");           

        getMimeMappingMethodInfo = mimeMappingType.GetMethod("GetMimeMapping", BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Public);

        if (getMimeMappingMethodInfo == null)
            throw new SystemException("Couldnt find GetMimeMapping method");

        if (getMimeMappingMethodInfo.ReturnType != typeof(string))
            throw new SystemException("GetMimeMapping method has invalid return type");

        if (getMimeMappingMethodInfo.GetParameters().Length != 1 && getMimeMappingMethodInfo.GetParameters()[0].ParameterType != typeof(string))
            throw new SystemException("GetMimeMapping method has invalid parameters");
    }

    public static string GetMimeType(string fileName)
    {
        lock (locker)
        {
            return (string)getMimeMappingMethodInfo.Invoke(null, new object[] { fileName });
        }
    }
}
#else // .NET 4.5 or later
public static class MimeExtensionHelper
{
    public static string GetMimeType(string fileName)
    {
        return MimeMapping.GetMimeMapping(fileName);
    }
}
#endif

同样在。net 4.5之前的版本中，静态MimeMapping类拥有一个名为_mappingDictionary的静态实例(类型为MimeMapping. mimemappingdictionarybase)，您可以从反射请求该实例，以便添加可能还不支持的新的MIME-Types。

**使用MediaTypeNames类——>样本:MediaTypeNames. application . pdf **