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

# 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](https://docs.microsoft.com/windows-hardware/drivers/ifs/file-system-minifilter-drivers) section in the Installable File Systems Design Guide.