有可能从一个任务中获得成功的结果吗?当其中一个任务失败时?

Result 属性,因为它抛出。所以要有一个部分成功的结果 WhenAll 惠纳尔 它从不抛出,而是返回结果和异常 ValueTuple 结构。

public static Task<(T[] Results, Exception[] Exceptions)> WhenAllEx<T>(
    params Task<T>[] tasks)
{
    tasks = tasks.ToArray(); // Defensive copy
    return Task.WhenAll(tasks).ContinueWith(t => // return a continuation of WhenAll
    {
        var results = tasks
            .Where(t => t.Status == TaskStatus.RanToCompletion)
            .Select(t => t.Result)
            .ToArray();
        var aggregateExceptions = tasks
            .Where(t => t.IsFaulted)
            .Select(t => t.Exception) // The Exception is of type AggregateException
            .ToArray();
        var exceptions = new AggregateException(aggregateExceptions).Flatten()
            .InnerExceptions.ToArray(); // Flatten the hierarchy of AggregateExceptions
        if (exceptions.Length == 0 && t.IsCanceled)
        {
            // No exceptions and at least one task was canceled
            exceptions = new[] { new TaskCanceledException(t) };
        }
        return (results, exceptions);
    }, default, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Default);
}

var tPass1 = Task.FromResult(1);
var tFail1 = Task.FromException<int>(new ArgumentException("fail1"));
var tFail2 = Task.FromException<int>(new ArgumentException("fail2"));

var task = WhenAllEx(tPass1, tFail1, tFail2);
task.Wait();
Console.WriteLine($"Status: {task.Status}");
Console.WriteLine($"Results: {String.Join(", ", task.Result.Results)}");
Console.WriteLine($"Exceptions: {String.Join(", ", task.Result.Exceptions.Select(ex => ex.Message))}");

输出:

状态:RANTO完成
结果:1
异常:故障1,故障2

也许 吧

public async Task<Task[]> RejectFailedFrom(params Task[] tasks)
{
    try
    {
        await Task.WhenAll(tasks);
    }
    catch(Exception exception)
    {
        // Handle failed tasks maybe
    }

    return tasks.Where(task => task.Status == TaskStatus.RanToCompletion).ToArray();
}

用法

var tasks = new[]
{
    Task.FromResult(1),
    Task.FromException<int>(new ArgumentException("fail1")),
    Task.FromException<int>(new ArgumentException("fail2"))
};

var succeed = await RejectFailedFrom(tasks);
// [ tasks[0] ]

玩弄@Theodor Zoulias的有力和优雅 solution Task.WhenAll _ => { } )以及 Wait

var cts = new CancellationTokenSource();
cts.Cancel();
var canceled = Task.Run(() => 1, cts.Token);

var faulted = Task.FromException<int>(new Exception("Some Exception"));

var ranToCompletion = Task.FromResult(1);

var allTasks = new[] { canceled, faulted, ranToCompletion };

// wait all tasks to complete regardless anything
Task.WhenAll(allTasks).ContinueWith(_ => { }).Wait();

foreach(var t in allTasks)
{
    Console.WriteLine($"Task #{t.Id} {t.Status}");
    if (t.Status == TaskStatus.Faulted)
        foreach (var e in t.Exception.InnerExceptions)
            Console.WriteLine($"\t{e.Message}");
    if (t.Status == TaskStatus.RanToCompletion)
        Console.WriteLine($"\tResult: {t.Result}");
}

输出如下所示:

Task #2 Canceled
Task #1 Faulted
        Some Exception
Task #5 RanToCompletion
        Result: 1

改变

var task = Task.WhenAll(tPass1, tFail1, tFail2);
task.Wait();

到

var all = new Task<int>[] { tPass1, tFail1, tFail2 }
    .Where(t => t.Status == TaskStatus.RanToCompletion);
var task = Task.WhenAll(all);
task.Wait();

Working example