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Cooperative cancellation

Context: Cancellation in .NET is cooperative: the called code must periodically check the token and respond. It is not forced or immediate.

using System.Threading;
using System.Threading.Tasks;

public class LongRunningTask
{
    public async Task RunAsync(CancellationToken token)
    {
        for (int i = 0; i < 1000000; i++)
        {
            if (token.IsCancellationRequested)
            {
                // Perform any cleanup
                return;
            }
            await Task.Delay(1);
        }
    }
}

Best practices

Check the token at logical points (loop start, after long operations).
Use ThrowIfCancellationRequested for simple cancellation.
Do not ignore cancellation requests.

Real-world usage example

File processing: Cancel reading a large file when the user aborts the operation.

Example: Cooperative cancellation sample