C# 立即返回 Task<bool>
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Return Task<bool> instantly
提问by Vitalii Vasylenko
I have a list of tasks, which i'd like to wait for. I'm waiting like
我有一个任务列表，我想等待。我在等
await TaskEx.WhenAll(MyViewModel.GetListOfTasks().ToArray());
MyViewModel.GetListOfTasks() returns List of Task:
MyViewModel.GetListOfTasks() 返回任务列表：
var tasksList = new List<Task>();
foreach (var item in Items)
{
tasksList.Add(item.MyTask());
}
Now, i'd like to return dummy task, which would be done immediately. However, TaskEx.WhenAll would wait it forever:
现在，我想返回虚拟任务，该任务将立即完成。但是， TaskEx.WhenAll 会永远等待它：
public Task<bool> MyTask()
{
return new Task<bool>(() => false);
}
How can i return Task, which would be finished instantly?
我怎样才能返回任务，它会立即完成？
采纳答案by David L
in .NET 4.5 you can use FromResult to immediately return a result for your task.
在 .NET 4.5 中，您可以使用 FromResult 立即返回任务的结果。
public Task<bool> MyTask()
{
return TaskEx.FromResult(false);
}
http://msdn.microsoft.com/en-us/library/hh228607%28v=vs.110%29.aspx
http://msdn.microsoft.com/en-us/library/hh228607%28v=vs.110%29.aspx
For Windows Phone 8.1 and higher, the API has been mergedto be consistent with other platforms:
对于 Windows Phone 8.1 及更高版本，已合并 API以与其他平台保持一致：
public Task<bool> MyTask()
{
return Task.FromResult(false);
}
回答by Sam Harwell
Prior to .NET 4.5, you can use TaskCompletionSource<TResult>to simulate the FromResultmethod.
在 .NET 4.5 之前，您可以使用TaskCompletionSource<TResult>来模拟该FromResult方法。
public static Task<TResult> FromResult<TResult>(TResult result)
{
var completionSource = new TaskCompletionSource<TResult>();
completionSource.SetResult(result);
return completionSource.Task;
}
