How to use SysInternal Handle to identify which object in the code has locked the "Test File.pdf" file

Question

I need to know how I can use Handle to identify which object in the code has locked the pdf file.

I generated pdf file with crystal reports in the background, email pdf to the recipients and then wanted to delete the file but was keep getting this message

 System.IO.IOException: The process cannot access the file 'c:\test\First Report for test.pdf' because it is being used by another process.
       at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
       at System.IO.File.InternalDelete(String path, Boolean checkHost)
       at System.IO.File.Delete(String path)

I disposed ReportDocument & SmtpClient object but that did not help, then I tried ProcessExplorer and command line handle with following command

C:\Users\demouser\SysinternalsSuite> handle test\First Report for test.pdf

and that did not help either. I examined the code again and resolved the issue by calling dispose method of MailMessage

So I am wondering if handle could be used in the first instance to identify locking object in the code.