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---
page_type: sample
description: "A minifilter demonstrating the use of cancel-safe queues."
languages:
- cpp
products:
- windows
---

<!---
    name: CancelSafe File System Minifilter Driver
    platform: WDM
    language: cpp
    category: FileSystem
    description: A minifilter demonstrating the use of cancel-safe queues.
    samplefwlink: http://go.microsoft.com/fwlink/p/?LinkId=617645
--->

# CancelSafe File System Minifilter Driver

The CancelSafe filter is a sample minifilter that you use if you want to use cancel-safe queues.

## Universal Windows Driver Compliant

This sample builds a Universal Windows Driver. It uses only APIs and DDIs that are included in OneCoreUAP.

Design and Operation
--------------------

The *CancelSafe* minifilter initializes a cancel-safe queue when it is attached to a volume. When the minifilter is deployed, it monitors read operations that are passing through the I/O stack. If the read operation is being performed on a file named csqdemo.txt, it is queued onto the cancel-safe queue. Queued operations are completed after a brief pause through a separate worker thread that is running in system context.

For more information on file system minifilter design, start with the [File System Minifilter Drivers](http://msdn.microsoft.com/en-us/library/windows/hardware/ff540402) section in the Installable File Systems Design Guide.