Unable to delete file locked by same process -- weird!

Question

I have an application written in PHP that uses a COM dll written in C#. The dll creates an image file by combining two other image files. The PHP script then takes over to do the housekeeping tasks of deleting the two source files and renaming the resulting combined file.

The problem is the PHP script can't delete one of the source files because it's locked. The weird thing is that the process that has it locked is itself which in this case is the Apache Web Server.

I have tried altering the C# dll to dispose of all bitmap and graphics objects prior to exiting, and yet the lock remains. My question is, what can I do to get the dll to let go and release the file locks. This is very frustrating.

Answer 1

To be sure that you're definitely getting rid of all potential locks on the image, you could wrap your code in a using block.

using(Bitmap myBitmap = new Bitmap())
{
  //use myBitmap in here
}

Answer 2

An application can definitely lock a file from itself. For example:

using(FileStream fs = File.Open("somefile.txt", FileMode.Open))
{
    File.Delete("somefile.txt"); // Exception: File already in use.
}

You need to make sure your all open handles to the file have been closed before your PHP file can clean up.

Answer 3

As a last resort you can use Unlocker utility (via command line) to unlock the files.