c# - 等待另一个任务的异步任务

Question

我有这样的代码:

private async Task<bool> DoAsyncThing()
{
  await doOtherThings();
} 

private async Task<bool> DoAsyncThing2()
{
  await doOtherThings2();
} 

private async Task<bool> SaveAll()
{
   return await _context.SaveChangesAsync() > 0;
}

public async Task<bool> FirstBatchProcess()
{
    var tasks = new List<Task<bool>>();
    ...
    users.Foreach(user => {
        task.Add(this.DoAsyncThing());
    });
    await Task.WhenAll(tasks);
    return await this.SaveAll();
}

public async Task<bool> SecondBatchProcess()
{
    // get all data from batch 1 and then do calculation
    var tasks = new List<Task<bool>>();
    ...
    users.Foreach(user => {
        task.Add(this.DoAsyncThing2());
    });
    await Task.WhenAll(tasks);
    return await this.SaveAll();
}


public async Task<bool> ProcessAll()
{
    await this.FirstBatchProcess();
    await this.SecondBatchProcess();
}

在 ProcessAll 中，我希望先完成 firstBatchProcess，然后再执行 SecondBatchProcess。因为我有一些来自 FirstBatchPROcess 的数据，稍后将在 SecondBatchProcess 中使用。如果我运行此代码，两者都将异步执行并导致错误，因为 SecondBatchProcess 需要从 FirstBatchProcess 生成的数据。

注意:两个 BatchProcesses 都包含多个异步循环，所以我使用 Task.WhenAll()如何等待 FirstBatchProcess 完成然后执行 SecondBatchProcess ？

Answer 1

更新

so when I call Task.Wait() it will waiting this task to be done then it will continue another process ?

既然你编辑了你的问题，如果我理解正确(我在字里行间)

await this.FirstBatchProcess();  // will wait for this to finish
await this.SecondBatchProcess(); // will wait for this to finish

答案是肯定的，所有在 FirstBatchProcess 中启动的任务都会在它执行 SecondBatchProcess 之前完成

原创

Task.WhenAll Method

Creates a task that will complete when all of the supplied tasks have completed.

我认为您可能对 await 运算符感到困惑

await (C# Reference)

The await operator is applied to a task in an asynchronous method to insert a suspension point in the execution of the method until the awaited task completes. The task represents ongoing work.

它实际上在等待!

Your Full Demo Here

private static async Task DoAsyncThing()
{
    Console.WriteLine("waiting");
    await Task.Delay(1000);
    Console.WriteLine("waited");
}

private static async Task SaveAll()
{
    Console.WriteLine("Saving");
    await Task.Delay(1000);
}

public static async Task ProcessAll()
{
    var tasks = new List<Task>();
    for (int i = 0; i < 10; i++)
    {
        tasks.Add(DoAsyncThing());
    }

    await Task.WhenAll(tasks);
    await SaveAll();
    Console.WriteLine("Saved");
}

public static void Main()
{
    ProcessAll().Wait();
    Console.WriteLine("sdf");
}

输出

waiting
waiting
waiting
waiting
waiting
waiting
waiting
waiting
waiting
waiting
waited
waited
waited
waited
waited
waited
waited
waited
waited
waited
Saving
Saved
sdf

所有任务都已完成。