File.Encrypt throwing "Parameter is incorrect"

Question

When I try to call System.IO.File.Encrypt() on an existing file, it throws a generic IOException, and the message is "Parameter is incorrect".

System.IO.File.Encrypt("C:\Project\StorageDirectory\file.txt")

The current user the process is running under has full control to the "StorageDirectory" folder. Is there something I'm missing permissions-wise?

Answer 1

Well reading the MSDN page,

An I/O error occurred while opening the file.

-or-

This operation is not supported on the current platform.

Neither is a particularly useful statement, but they should give you somewhere to start.

• Can you read the file? Have you tested it from within your app?

• Have you done encryption elsewhere? I've never seen encryption fail like that before (but there's always a first time!)

Answer 2

The docs say this could be caused by

An I/O error occurred while opening the file. -or- This operation is not supported on the current platform.

It could be that the file is locked by another process, or that you don't have permission to modify it. You could run ProcMon while you reproduce this error to see if that's your problem.

Answer 3

You need to escape the backslash characters (notice the @ character)

System.IO.File.Encrypt(@"C:\Project\StorageDirectory\file.txt")