`await Task.WhenAll` vs. Multiple Awaits: Which is the Preferred Method for Handling Multiple Asynchronous Tasks?

The preferred method for asynchronous task completion: Comparison of single await Task.WhenAll and multiple await

In asynchronous programming, when handling multiple tasks, developers often need to choose between using a single await Task.WhenAll statement or executing multiple await statements in sequence. This article explores the advantages of using await Task.WhenAll over multiple awaits, especially in scenarios where the order in which tasks are completed is not important.

The following code snippet shows both methods:

<code class="language-csharp">// 使用多个 await
static async Task DoWork1()
{
    var t1 = DoTaskAsync("t1.1", 3000);
    var t2 = DoTaskAsync("t1.2", 2000);
    var t3 = DoTaskAsync("t1.3", 1000);

    await t1; await t2; await t3;

    Console.WriteLine("DoWork1 results: {0}", String.Join(", ", t1.Result, t2.Result, t3.Result));
}

// 使用 await Task.WhenAll
static async Task DoWork2()
{
    var t1 = DoTaskAsync("t2.1", 3000);
    var t2 = DoTaskAsync("t2.2", 2000);
    var t3 = DoTaskAsync("t2.3", 1000);

    await Task.WhenAll(t1, t2, t3);

    Console.WriteLine("DoWork2 results: {0}", String.Join(", ", t1.Result, t2.Result, t3.Result));
}</code>

Why is await Task.WhenAll better than multiple await?

1. Error propagation: await Task.WhenAll collects all errors from various tasks and propagates them as AggregateException. This ensures that if one or more tasks fail, no errors are lost. Multiple await will hide errors when the previous await throws an exception.

2. Guaranteed Completion: await Task.WhenAll Guarantees that all tasks will be completed before their return, even if some tasks have errors or been cancelled. This is especially useful when your code relies on the results of all tasks being available.

3. Simplify your code: Use await Task.WhenAll to make the semantics of waiting for multiple tasks explicit in your code, improving readability and reducing the risk of concurrency-related bugs.

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