title: How Can I get Mime Type in IOS which is not based on extension
body: <p>we know that we can get the file's MIME TYPE from the file's extension,but it's not exactly.for example we changed the file's extension and we will get the wrong mime type.
  and also we know the way that get the mime type by a file signature in C#,(using the urlmon.dll <a href="https://stackoverflow.com/questions/58510/using-net-how-can-you-find-the-mime-type-of-a-file-based-on-the-file-signature).But">Using .NET, how can you find the mime type of a file based on the file signature not the extension</a> ,my question is that how can we get the exact mime type in IOS,no matter the file's extension is changed by someone,we can getthe right mime type.</p>
  
  <p>thank you for your attention~!</p>