C# 等待任务列表
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Await for list of Tasks
提问by ctlaltdefeat
I'm trying to do something like this:
我正在尝试做这样的事情：
foreach (var o in ObjectList)
{
CalculateIfNeedToMakeTaskForO(o);
if (yes)
TaskList.Add(OTaskAsync());
}
Now I would like to wait for all these tasks to complete. Besides doing
现在我想等待所有这些任务完成。除了做
foreach(var o in ObjectList)
{
Result.Add("result for O is: "+await OTaskAsync());
}
Is there anything I could do? (better, more elegant, more "correct")
有什么我可以做的吗？（更好，更优雅，更“正确”）
采纳答案by Simon Belanger
You are looking for Task.WaitAll(assuming your TaskListimplemented IEnumerable<Task>)
您正在寻找Task.WaitAll（假设您已TaskList实现IEnumerable<Task>）
Task.WaitAll(TaskList.ToArray());
Edit:Since WaitAllonly takes an array of task (or a list of Taskin the form of a variable argument array), you have to convert your Enumerable. If you want an extension method, you can do something like this:
编辑：由于WaitAll只需要一个任务数组（或Task一个可变参数数组形式的列表），你必须转换你的 Enumerable。如果你想要一个扩展方法，你可以这样做：
public static void WaitAll(this IEnumerable<Task> tasks)
{
Task.WaitAll(tasks.ToArray());
}
TaskList.WaitAll();
But that's really only syntactic sugar.
但这实际上只是语法糖。
回答by Stephen Cleary
You are looking for Task.WhenAll:
您正在寻找Task.WhenAll：
var tasks = ObjectList
.Where(o => CalculateIfNeedToMakeTaskForO(o))
.Select(o => OTaskAsync(o))
.ToArray();
var results = await Task.WhenAll(tasks);
var combinedResults = results.Select(r => "result for O is: " + r);
