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c#asynchronous

How to make an asynchronous method return a value?

I know how to make asynchronous methods but say I have a method that does a lot of work and then returns a boolean value?

How should I return the boolean value on the callback?

Clarification:

public bool Foo()
{
    Thread.Sleep(100_000); // Do work.
    return true;
}

I want to be able to make this asynchronous.

Solution

  • There are a few ways of doing that... the simplest is to have the async method also do the follow-on operation. Another popular approach is to pass in a callback, i.e.

    void RunFooAsync(..., Action<bool> callback) {
     // do some stuff
     bool result = ...

     if(callback != null) callback(result);
}

    Another approach would be to raise an event (with the result in the event-args data) when the async operation is complete.

    Also, if you are using the TPL, you can use ContinueWith:

    Task<bool> outerTask = ...;
outerTask.ContinueWith(task =>
{
    bool result = task.Result;
    // do something with that
});