IsCancellationRequested

**IsCancellationToken** is a class in the .NET framework that represents a flag used to coordinate cancellation across thread boundaries in asynchronous operations. Introduced in .NET 4.5, it plays a key role in implementing cooperative cancellation, allowing threads to respond gracefully to cancellation requests without abrupt termination.

The class is part of the `System.Threading` namespace and is typically used alongside `CancellationTokenSource`, which generates tokens that can be canceled. A `CancellationToken` can be passed to asynchronous methods (such as `Task`, `Task<T>`, or `IAsyncOperation`) to enable cancellation. When a token is canceled, it raises a `TaskCanceledException` in the associated task, signaling the operation to halt.

Key features include:

- **Thread-safe operation**: Tokens can be safely shared across threads.

- **Cooperative cancellation**: Only methods explicitly checking the token will respond to cancellation.

- **Combining tokens**: Multiple tokens can be combined using `CancellationTokenSource.CreateLinkedTokenSource` to monitor multiple cancellation requests.

Common use cases include long-running operations (e.g., file downloads, database queries) where cancellation is desirable for performance or user experience reasons. Developers often implement cancellation checks using `token.ThrowIfCancellationRequested()` or `await Task.WhenAny(task, token.WaitHandle.WaitAsync())`.

While cancellation is cooperative, it does not prevent thread termination—only the cancellation-aware code will halt. Unmanaged resources should be released separately to avoid leaks. The pattern is widely adopted in modern .NET applications for robust asynchronous workflows.