title: Is there any way to validate file content before upload?
body: <p>I did coding for file upload in <code>asp.net</code> and validating a file extension (only png)</p>
  
  <p>If user renames the file (before upload) from other to png (like pdf to png) then that file will valid as png because I just validate extension.</p>
  
  <p>Is there any 3rd party API or service to validate file extension with valid content?</p>
  
  <p>Thanks in advance </p>