无法将布尔类型隐式转换为System.Threading.Tasks.Task <bool>

Question

I'm tying to follow the async await structure as described on msdn here

So I have an async task:

    public async void Starter()
    {

        CC = new CustomClass();

        Task<bool> newTask = CC.MethodThatReturnsBool();

        // DO SOME VISUAL THINGS

        bool b = await newTask;

        }
    }

But I'm getting a compile-stopping error around the CC.MethodThatReturnsBool(); as shown by my question header.

How do I get my bool in the right format? I tried randomly casting (Task) in front of the erroneous method call but it just removed the "implicitly" from my error message!

I'm using:

VS Community 2017 and .NET Framework 4.7

Answer 1

According to the error, this returns a bool :

CC.MethodThatReturnsBool()

So you'd store it as such:

bool newBool = CC.MethodThatReturnsBool();

Which, it would seem, means that there are no asynchronous operations to be awaited. Simplifying:

public void Starter()
{
    CC = new CustomClass();

    bool b = CC.MethodThatReturnsBool();

    // do something with your bool?
}

It's not clear why you're expecting to await anything, and there may indeed be more to this that you're not showing, but if the method you're calling is synchronous then there's no need to await it.

Side note: async void is a really bad idea . It only exists for compatibility with UI event handlers and such. If you're writing anything that you control, don't use async void .

---

Edit:

Based on your update to the question, it sounds like what's happening here is that you have a long-running synchronous process that you'd like to not block the UI thread? You can wrap something in a Task , perhaps something like this:

bool b = await Task.Run(() => new CustomClass().MethodThatReturnsBool());

So perhaps overall you're looking for something more like this (untested)?:

public async Task Starter()
{
    Task<bool> newTask = Task.Run(() => new CustomClass().MethodThatReturnsBool());

    // DO SOME VISUAL THINGS

    bool b = await newTask;

    // do something with your bool?
}

To elaborate on a previous point, note that the overall method is now async Task instead of async void . This makes Starter itself awaitable, as void otherwise would not be.

Ideally of course, MethodThatReturnsBool should itself be async if it is internally performing various I/O bound operations which cause its delay. (As implied in your comment on the question above.) That may involve refactoring elsewhere in the system, but in the long run is the preferable approach.