从文件扩展名获取MIME类型

本文翻译自：Get MIME type from filename extension

如何从文件扩展名中获取MIME类型？

#1楼

参考：https://stackoom.com/question/4Jsi/从文件扩展名获取MIME类型

#2楼

You can find that information in the registry. 您可以在注册表中找到该信息。 For instance, the MIME type for .pdf file can be found in the key HKEY_CLASSES_ROOT\\.pdf , in the value "Content Type" : 例如，.pdf文件的MIME类型可以在密钥HKEY_CLASSES_ROOT\\.pdf中找到，值为“内容类型”：

string mimeType = Registry.GetValue(@"HKEY_CLASSES_ROOT\.pdf", "Content Type", null) as string;

#3楼

You could use the table provided from Apache 's httpd. 你可以使用Apache的httpd提供的表。 It should be trivial to map this into a function, dictionary, list, etc. 将它映射到函数，字典，列表等应该是微不足道的。

Also, as seen here , extension->mime type is not necessarily a function. 此外，由于看到这里，扩展- > MIME类型不一定是功能。 There may be multiple common MIME types per file extension, so you should look at the requirements of your application, and see why you care about MIME types, what you want "to do" with them, etc. Can you use file extensions to key the same behavior? 每个文件扩展名可能有多种常见的MIME类型，因此您应该查看应用程序的要求，并了解您关心MIME类型的原因，您希望与它们“做什么”等等。您可以使用文件扩展名来键入同样的行为？ Do you need to read the first few bytes of a file to determine its MIME type as well? 您是否需要读取文件的前几个字节以确定其MIME类型？

#4楼

For ASP.NET or other 对于ASP.NET或其他

The options were changed a bit in ASP.NET Core, here they are ( credits ): 这些选项在ASP.NET Core中有所改变，在这里它们是（学分）：

new FileExtensionContentTypeProvider().TryGetContentType(fileName, out contentType); (vNext only) （仅限vNext）
- Never tested, but looks like you can officially expand the mime types list via the exposed Mappings property. 从未测试过，但看起来你可以通过暴露的Mappings属性正式扩展mime类型列表。
Use the MimeTypes NuGet package 使用MimeTypes NuGet包
Copy the MimeMappings file from the reference source of the .NET Framework 从.NET Framework的引用源复制MimeMappings文件

For .NET Framework >= 4.5: 对于.NET Framework> = 4.5：

Use the System.Web.MimeMapping.GetMimeMapping method, that is part of the BCL in .NET Framework 4.5: 使用System.Web.MimeMapping.GetMimeMapping方法，该方法是.NET Framework 4.5中BCL的一部分：

string mimeType = MimeMapping.GetMimeMapping(fileName);

If you need to add custom mappings you probably can use reflection to add mappings to the BCL MimeMapping class, it uses a custom dictionary that exposes this method, so you should invoke the following to add mappings (never tested tho, but should prob. work). 如果你需要添加自定义映射，你可以使用反射来为BCL MimeMapping类添加映射，它使用一个公开此方法的自定义字典，所以你应该调用以下内容来添加映射（从未测试过，但应该是prob。）。

Anyway, when using reflection to add MIME types, be aware that since you're accessing a private field, its name might change or even be totally removed, so you should be extra cautious and add double checks and provide fail safe action for every step. 无论如何，当使用反射添加MIME类型时，请注意，因为您正在访问私有字段，其名称可能会更改甚至完全删除，因此您应该格外谨慎并添加双重检查并为每个步骤提供故障安全操作。

MimeMapping._mappingDictionary.AddMapping(string fileExtension, string mimeType)

#5楼

FileExtension handle the file extension and not the Mime. FileExtension处理文件扩展名而不是Mime。 The user can change the file extension, so check the Mime. 用户可以更改文件扩展名，因此请检查Mime。 The codes examples associate Mime by file extension, this is wrong and does not work. 代码示例通过文件扩展名关联Mime，这是错误的，不起作用。

Need to get the contenttype file and check if the table Mime contetType this file according to the file extension. 需要获取contenttype文件并检查表Mime contetType根据文件扩展名contetType此文件。 Now, how to get the ContentType of the file? 现在，如何获取文件的ContentType ？

Using FileUpload is thus: FileUpload.PostedFile.ContentType; 因此使用FileUpload： FileUpload.PostedFile.ContentType; Now if I already have the file, as caught your ContentType? 现在，如果我已经拥有该文件，那么抓住了您的ContentType？

#6楼

Inspired by Samuel's answer, I wrote an improved version: 受Samuel的回答启发，我写了一个改进的版本：

Also works when extension is uppercase. 扩展名为大写时也可以。
Take filename as input, handle files without extensions gracefully. 将文件名作为输入，正常处理没有扩展名的文件。
Don't include "." 不要包含“。” in keys. 在钥匙。
List from Apache , for which I wrote a small transformation script . 来自Apache的列表，我为此编写了一个小的转换脚本。

The resulting source code is over 30K characters so I can't post it here, check it on Github . 结果源代码超过30K字符，所以我不能在这里发布，在Github上检查它。