使用 UI 时 DownloadStringTaskAsync 结果死锁

Question

这是我的代码：

Dim getUrlContentTask = Task.Factory.StartNew(Function() GetUrlContent(modifiedUrl))
getUrlContentTask.Wait()

'Check #6 - Check if the url has an expired text in it.
CheckIfExpired(getUrlContentTask)

Public Shared Function GetUrlContent(url As String) As task(of String)

    Try

        Dim webClient As New System.Net.WebClient
        Dim webContent = Await webClient.DownloadStringTaskAsync(url)

        Return webContent
End Function

Public Shared Function CheckIfExpired(webContent As Task(Of String) As Boolean

    If util.ExpiredTexts.Any(Function(o) webContent.Result.Contains(o)) = False Then
        Throw New UriFormatException("Url leads to an expired page")
    End If

    Return True
End Function

当此函数运行没有 UI 时它运行很好，但是当我尝试通过 UI 运行它时它卡住了 webContent.Result.contains(o)

如何使用 UI 使其工作？

Answer 1

您正在 UI 线程上死锁，因为 Task.Result 正在阻塞。您需要改用 async-await。

将您的函数更改为 return Task(Of String)，将 Async 关键字和 Async 后缀添加到函数名称（这是命名约定）：

Public Shared Async Function GetUrlContentAsync(url As String) As Task(Of String)
    Try

        Dim webClient As New System.Net.WebClient
        Dim webContent = Await webClient.DownloadStringTaskAsync(url)

        Return webContent
        End Function

使用 UI 时 DownloadStringTaskAsync 结果死锁

DownloadStringTaskAsync Result DeadLock when using UI

vb.net

parallel-processing

deadlock

asynchronous

async-await