与 Promise.all 等效的 C# 是什么？

Question

I would like to fetch data from multiple locations from Firebase Realtime Database like described here and here by Frank van Puffelen and I can't find any equivalent to Promise.all in c#. What would be the proper way to do it?

Answer 1

That you are looking for is Task.WhenAll . You should create as many tasks as the multiple locations from which you want to fetch your data and then feed them in this method.

Answer 2

To expand on @Christos's accepted answer:

Task.WhenAll appears to be about as close as you will get for a drop-in replacement for Promise.all . I actually found it to be closer than I initially thought. Here's an example using a JavaScript Promise.all implementation that you may want to replicate in C#:

const [ resolvedPromiseOne, resolvedPromiseTwo ] = await Promise.all([ taskOne, taskTwo ]);

In C# you can do something very similar with Task.WhenAll (assuming they return the same types).

var taskList = new[]
{
  SomeTask(),
  AnotherTask()
};

var completedTasks = await Task.WhenAll(taskList);

// then access them like you would any array
var someTask = completedTasks[0];
var anotherTask = completedTasks[1];

// or just iterate over the array
foreach (var task in completedTasks)
{
  doSomething(task);
}

This assumes they're both in async methods / functions.