Pdm API: Error unlocking a .SLDRW

Hi,
I am making a C# StandAlone macro that unlock every file that are locked by the active user.
I browse every folder of the vault to find the files to unlock and add them to a IEdmBatchUnlock2.

The problem occurs when I use IEdmBatchUnlock2.CreateTree(). Exception thrown: "The file format is not recognized".

I have also tried to use IEdmFile17.UnlockFile() method and i have the same error. The drawing is not open in solidworks and is not in a local/private state.

Thank you for your help.