FileStream Create error in Delphi

I’ll share some tip on File Creation in Delphi. Some day I had to make a solution to create same file stream a lot times in a cycle and to show it at regular intervals (it was opened in another application). Well, if file is already created and time interval get’s too short, you might get an exception, that file is "in use on another process" and even setting file permissions doesn’t help:

   1: var File : TFileStream 

   2: File := TFileStream.Create(OutputFile, fmCreate or fmShareExclusive)

The solution is, first to check out if file is in use. We could use Windows API CreateFile function for this task:

   1: function IsFileInUse(FileName: TFileName): Boolean;

   2:   var HFileRes: HFILE;

   3: begin

   4:   Result := False;

   5:   if not FileExists(FileName) then Exit;

   6:   HFileRes := CreateFile( PChar(FileName), //Windows API Create

   7:     GENERIC_READ or GENERIC_WRITE, 0, nil, OPEN_EXISTING,

   8:     FILE_ATTRIBUTE_NORMAL, 0);

   9:   Result := (HFileRes = INVALID_HANDLE_VALUE);

  10:   //returns false File handle if file is in use

  11:   if not Result then CloseHandle(HFileRes); //Deny and close handle

  12: end;

Then you can check if file is in use:

   1: if NOT IsFileInUse(OutputFile)

   2:    then File := TFileStream.Create(OutputFile, fmCreate or  fmShareExclusive);

update: Zarko Gajis from About.com made another universal function for checking if "FileIsInUse" here:

Programmatically Check If File is In Use – Delphi Code