How the separation of CancellationToken and CancellationTokenSource is useful?

[falsandtru]

Seems like that separation make no restriction. Everyone can cancel any token. Another, should I post the comment to the mailing list in place of here?

[rbuckton]

I'm not sure I understand what you mean. Only the CancellationTokenSource can cancel its token. You do not pass the CancellationTokenSource to a callee, just the token. For example:

const source = new CancellationTokenSource();
otherAsyncFn(source.token); // receives the token, does not have access to the source.
source.cancel(); // only the source can cancel

[falsandtru]

Sorry, I thought the following code output 0, 1, 2, but it actually outputs 1, 2. It has no problem I thought. Thanks for the response!

const token = new CancellationToken();
const source = new CancellationTokenSource([token]);
token.register(() => console.log(0));
source.token.register(() => console.log(1));
new CancellationTokenSource([source.token]).token.register(() => console.log(2));
source.cancel();