運行多個等候在同一時間

Question

我有一個看起來像這樣的代碼：

firstList = await GetFirstListFilesAsync(); 
textBlock1.Text = "found " + firstList.Count + " first list's results"; 
secondList = await GetSecondListFilesAsync(); 
textBlock2.Text = "found " + secondList.Count + " second list's results"; 
thirdList = await GetThirdListFilesAsync(); 
textBlock3.Text = "found " + thirdList.Count + " third list's results" 

所以，現在它被第一個列表，將第一TextBlock文本，然後它得到第二個列表，設置第二TextBlock文字和然後獲取第三個列表並設置第三個TextBlock文本。但我希望所有等待的操作都能同時運行，因此所有TextBlock s都會同時更新或更新。或者可能不是在同一時間 - 每個TextBlock會隨着相應的等待方法完成而更新。無論如何，我想在這裏實現的目標是更快地獲得結果。如果我一個接一個地運行這些方法，他們會一直等到前一個結束，但如果它們同時運行，第三個方法會更快地返回結果，對嗎？所以我的問題是 - 這可能嗎？如果是，那麼如何？

Answer 1

我認爲這是你在找什麼：

var tasks = new Task<MyMethodReturnObject>[3]; 
tasks[0] = GetFirstListFilesAsync(); 
tasks[1] = GetSecondListFilesAsync(); 
tasks[2] = GetThirdListFilesAsync(); 

// At this point, all three tasks are running at the same time. 

// Now, we await them all. 
await Task.WhenAll(tasks); 

// Get an individual result, where result is MyMethodReturnObject 
var myText = tasks[0].Result; 

// Loop through results 
var results = tasks.Select(o => o.Result).ToList(); 
foreach (var result in results) 
{ 
    Console.Write(result); 
} 

來源：http://blog.stephencleary.com/2012/02/async-and-await.html

Answer 2

您可以嘗試將工作轉移到Task的集合中，並使用Task.WaitAll來加入線程。

Answer 3

使用大衛的回答還是一樣把所有的等待在一起，然後調用設置文本值這樣簡單：

firstList = await GetFirstListFilesAsync(); 
secondList = await GetSecondListFilesAsync(); 
thirdList = await GetThirdListFilesAsync(); 

textBlock1.Text = "found " + firstList.Count + " first list's results"; 

textBlock2.Text = "found " + secondList.Count + " second list's results"; 

textBlock3.Text = "found " + thirdList.Count + " third list's results" 

Answer 4

只需將創建爲即可他們：

var firstWait = GetFirstListFilesAsync(); 
var secondWait = GetSecondListFilesAsync(); 
var thirdWait = GetThirdListFilesAsync(); 
firstList = await firstWait; 
textBlock1.Text = "found " + firstList.Count + " first list's results"; 
secondList = await secondWait ; 
textBlock2.Text = "found " + secondList.Count + " second list's results"; 
thirdList = await thirdWait ; 
textBlock3.Text = "found " + thirdList.Count + " third list's results"; 

這仍然不會顯示任何結果，直到第一項已完成，但允許並行地取得進展。如果你想處理每一個作爲它在一個單一的功能內完成，因爲你必須WaitAny關於awaitables的集合，然後確定（手動）哪一個已完成，從那裏刪除那些收集和循環，直到所有完成。

Answer 5

所以你不想分組await塊，你想要指定完成後會發生什麼。

GetFirstListFilesAsync().ContinueWith(task => { 
    textBlock1.Text = "found " + task.Result.Count + " first list's results"; 
}); 
GetSecondListFilesAsync().ContinueWith(task => { 
    textBlock2.Text = "found " + task.Result.Count + " second list's results"; 
}); 
GetThirdListFilesAsync().ContinueWith(task => { 
    textBlock3.Text = "found " + task.Result.Count + " third list's results"; 
}); 

這樣會做到這一點的最快方法，因爲一旦Task完成後，您textBlock.Text將被設置，他們將不會在上一代人來完成等待。

Answer 6

我希望所有等待的操作都會同時運行，所以所有的TextBlocks都會同時更新或更新。或者可能不在同一時間 - 每個TextBlock將會隨着相應的await方法完成而更新。

然後定義了一些新的方法：

private async Task<TFirst> GetFirstListFilesAndDisplayAsync() 
{ 
    var firstList = await GetFirstListFilesAsync(); 
    textBlock1.Text = "found " + firstList.Count + " first list's results"; 
} 

private async Task<TSecond> GetSecondListFilesAndDisplayAsync() 
{ 
    var secondList = await GetSecondListFilesAsync(); 
    textBlock2.Text = "found " + secondList.Count + " second list's results"; 
} 

private async Task<TThird> GetThirdListFilesAndDisplayAsync() 
{ 
    var thirdList = await GetThirdListFilesAsync(); 
    textBlock3.Text = "found " + thirdList.Count + " third list's results"; 
} 

然後同時打電話給他們所有：

var firstTask = GetFirstListFilesAndDisplayAsync(); 
var secondTask = GetSecondListFilesAndDisplayAsync(); 
var thirdTask = GetThirdListFilesAndDisplayAsync(); 

await Task.WhenAll(firstTask, secondTask, thirdTask); 

firstList = await firstTask; 
secondList = await secondTask; 
thirdList = await thirdTask;