encrypt minifilter can't work for offline files

I have developped a minifilter for encrypt on the fly.
It works well for local files and remote files.
But when the offline folders is on,everything is strange.

In my opinion,the offline files is the feature supportted by RDR.
When the network is down,the application open a file(the file is in offline folder),RDR will open a corresponding file in C:\windows\CSC(Yes,RDR will open many file in C:\windows\CSC) by a system thread.
When the application read/write/set the file(the file is in offline folder),RDR will read/write/sett the corresponding file in C:\windows\CSC.

And,EFS is not on these offline files(that’s to say,don’t check “encrypte offline files for security”).So,I don’t think about EFS.

My solution in my minifilter is:
Skip all the files in C:\windows\CSC.
That’s to say,in pre-create,I don’t care the files in C:\windows\CSC;
So,I encrypt the file(on the fly) just on RDR(the deviceobject is RDR).
My FileTest works well for my solution.For example,Create a File and write it;Open a encrypted file(decrypt on the fly).

But,If I start Work(microsoft office Word),and save the doc in the offline folders(the network is down),Work will report “Disk is Full”.
…I’m puzzled…
Anybody can clear it?And what should I Do?

I have read all issues about it.I can’t get the answer.
And somebody say offline files can’t encrypted on the fly,just as compressed files.
I don’t think so.Yes,I can see the FSCTL_SET_COMPRESSION to the file in C:\windows\CSC,But the value is COMPRESSION_FORMAT_NONE!
I think it just for ensure the file(in c:\windows\CSC) is not compressed.

sorry for typeing mistake~~~not Work ,is Word

>>But,If I start Work(microsoft office Word),and save the doc in the offline
folders(the network is down),Work will report “Disk is Full”.

should be

>>But,If I start Word(microsoft office Word),and save the doc in the offline
folders(the network is down),Word will report “Disk is Full”.