Return value of the Async/Await method: Task or Void?

In asynchronous programming, whether the return value of the async method is Task or void has a significant impact. This article will explore the scenarios that each option applies.

Return Task

Usually, the async method should return Task. This allows the code await to be called and track its progress if necessary. The main exception to this rule is when you explicitly need the void return type, such as when handling events.

Return Void

Tag it as "Top-level asynchronous operation" using the void return type's method. These operations behave differently when exceptions occur. Unlike the Task of the return value, exceptions in the void asynchronous method are not observed by default. They become unhandled exceptions and may trigger the TaskScheduler.UnobservedTaskException handler.

public static async void AsyncMethod2(int num)
{
    await Task.Factory.StartNew(() => Thread.Sleep(num));
}

async and await keywords are unnecessary because the exception is not required to be handled explicitly. However, if an exception occurs, it will not be observed and may not be handled correctly.

Exception handling example]

Task and void asynchronous methods, consider the following code:

static async void f()
{
    await h();
}

static async Task g()
{
    await h();
}

static async Task h()
{
    throw new NotImplementedException();
}

f] is called, the exception is observed and treated as any other unhandled exception. However, if g] is called, the exception is never observed and will be handled by the TaskScheduler.UnobservedTaskException handler, which will result in undefined behavior.

Best Practices

Task from the async method unless you explicitly need the void return type. This ensures that the exception is handled correctly and that the caller can select await the task and track its progress.

async/await best practices: https://learn.microsoft.com/en-us/archive/msdn-magazine/2013/march/async-await-best-practices-in-asynchronous-programming