c# - 异步执行与预期不同

Question

在下面的片段中

    private async void FinishCommandExecute()
    {
        Console.WriteLine("FinishCommandExecute_1");
        _granularBlobAnalyzer.SaveResult(SampleID, Operator, Comments);
        Console.WriteLine("FinishCommandExecute_2");
        await Task.Run(() => FlushCommandExecute());
        Console.WriteLine("FinishCommandExecute_3");
        State = GBAState.IDLE;
        Console.WriteLine("FinishCommandExecute_4");
    }

    private async void FlushCommandExecute()
    {
        Console.WriteLine("FlushCommandExecute_1");
        State = GBAState.FLUSHING;
        Console.WriteLine("FlushCommandExecute_2");
        await Task.Run(() => _granularBlobAnalyzer.Flush()); // Task to wrap sync method
        Console.WriteLine("FlushCommandExecute_3");
        State = GBAState.STOPPED;
        Console.WriteLine("FlushCommandExecute_4");
    }

我调用 FinishCommandExecute(它作为命令绑定(bind)到一个按钮)，我希望 finish 命令 会调用 flush 命令 并等待它完成，但它不会等待 flush 命令中的等待...并且执行继续

如果您查看评论，我会期望控制台中出现以下内容

• FinishCommandExecute_1
• 完成命令执行_2
• FlushCommandExecute_1
• FlushCommandExecute_2
• FlushCommandExecute_3
• FlushCommandExecute_4
• 完成CommandExecute_3
• 完成CommandExecute_4

而实际是:

• FinishCommandExecute_1
• FinishCommandExecute_2
• FlushCommandExecute_1
• FlushCommandExecute_2
• 完成CommandExecute_3
• 完成CommandExecute_4
• FlushCommandExecute_3
• FlushCommandExecute_4

为什么在第二种异步方法中不异步等待任务运行

Answer 1

FlushCommandExecute 是一个async void，所以它运行未被观察到，你不能等待\等待它，除非你使用某种同步机制，如 AutoResetEvent 等，或重构您的代码以调用 async Task 并等待它。

private async void FlushCommandExecute() => await FlushCommand();

private async void FinishCommandExecute()
{
    ...
    await FlushCommand();
    ...
}

private async Task FlushCommand()
{
     ...
}