c# - 在 Singleton.Instance 后面调用异步方法

Question

我有一个基本的单例类，但是单例有一个像这样的异步方法:

public sealed class AddInHandler
{
    private static readonly AddInHandler instance = new AddInHandler();

    static AddInHandler()
    {
    }

    AddInHandler()
    {
    }

    public static AddInHandler Instance
    {
        get { return instance.Value; }
    }

    public async Task<AvailableActions> GetAvailableActions(string carrierMnemonic)
    {
        // some code that uses await...
    }
}

如果我尝试通过单例使用异步方法，例如:

public async Task<Collection<CarrierInformation>> RetrieveAvailableCarriersAsync()
{
    // some await code here

    await Task.Run(() => 
    {
        // ...
        var availableActions = await AddInHandler.Instance.GetAvailableActions(addIn.Name);
    }
}

然后我遇到了错误。

The 'await' operator can only be used within an async lambda expression. Consider marking this lambda expression with the 'async' modifier.

我预计是因为 Instance 属性不是异步的，所以我遇到了这个问题？这是否正确，是否有推荐的解决此问题的最佳方法？

Answer 1

I'm expecting it's because the Instance property isn't async that I'm having this issue?

不，您只是在 lambda 表达式声明中缺少 async 修饰符。 lambda 本身必须标记为 async 以便编译器在其中使用 await:

await Task.Run(async () => 
{
    // ...
    var availableActions = await AddInHandler.Instance.GetAvailableActions(addIn.Name);
}

The documentation非常简单:

Use the async modifier to specify that a method, lambda expression, or anonymous method is asynchronous. If you use this modifier on a method or expression, it's referred to as an async method.