由视图模型中的任务导致的内存泄漏

Question

我有以下代码，它会导致内存泄漏。

问题是任务，当我删除它时，一切都很好，视图和视图模型都是GCed的。似乎任务保留了对更新时间日期的引用，因此保留了视图模型。我尝试了各种方法，但没有一种奏效，希望有人有任何想法或解释为什么会这样。

public class HeaderViewModel : Observable, IDisposableAsync
{
public HeaderViewModel (IDateTimeProvider dateTimeProvider)
{
TokenSource = new CancellationTokenSource();
ATask = Task.Run(
async () =>
{
while(!TokenSource.Token.IsCancellationRequested)
{
UpdateTimeData();
await Task.Delay(800);
}
IsDisposed = true;
},
TokenSource.Token);
UpdateTimeData();
void UpdateTimeData()
{
TimeText = dateTimeProvider.Now.ToString("HH:mm:ss");
DateText = dateTimeProvider.Now.ToString("dd.MM.yyyy");
}
}
public CancellationTokenSource TokenSource { get; set; }
public bool IsDisposed { get; set; }
public string TimeText
{
get => Get<string>();
set => Set(value);
}
public string DateText
{
get => Get<string>();
set => Set(value);
}
private Task ATask { get; set; }
public async Task Dispose()
{
TokenSource.Cancel();
while(!IsDisposed)
{
await Task.Delay(50);
}
TokenSource.Dispose();
ATask.Dispose();
ATask = null;
TokenSource = null;
}
}

这是基于计时器的解决方案，它也会导致内存泄漏：

public class HeaderViewModel : Observable, IDisposableAsync
{
public HeaderViewModel(IDateTimeProvider dateTimeProvider)
{
DateTimeProvider = dateTimeProvider;
ATimer = new Timer(800)
{
Enabled = true
};
UpdateTimeData(this, null);
ATimer.Elapsed += UpdateTimeData;
}
public string TimeText
{
get => Get<string>();
set => Set(value);
}
public string DateText
{
get => Get<string>();
set => Set(value);
}
public bool IsDisposed { get; set; }
private IDateTimeProvider DateTimeProvider { get; }
private Timer ATimer { get; }
public async Task Dispose()
{
ATimer.Stop();
await Task.Delay(1000);
ATimer.Elapsed -= UpdateTimeData;
ATimer.Dispose();
IsDisposed = true;
}
private void UpdateTimeData(object sender, ElapsedEventArgs elapsedEventArgs)
{
TimeText = DateTimeProvider.Now.ToString("HH:mm:ss");
DateText = DateTimeProvider.Now.ToString("dd.MM.yyyy");
}
}

Answer 1

我找到了解决方案。感谢keuleJ，他发布了引导我的评论。因此，当您创建其中任何一个时，任务或计时器都会捕获 ViewModel 的实例。防止它的方法是制作弱引用并使用它：

public class HeaderViewModel : Observable, IDisposableAsync
{
public HeaderViewModel(IDateTimeProvider dateTimeProvider)
{
DateTimeProvider = dateTimeProvider;
UpdateTimeData();
var weakReference = new WeakReference(this);
Task.Run(
async () =>
{
while(!((HeaderViewModel)weakReference.Target).IsDisposing)
{
((HeaderViewModel)weakReference.Target).UpdateTimeData();
await Task.Delay(800);
}
((HeaderViewModel)weakReference.Target).IsDisposed = true;
});
}
public bool IsDisposed { get; set; }
public string TimeText
{
get => Get<string>();
set => Set(value);
}
public string DateText
{
get => Get<string>();
set => Set(value);
}
private IDateTimeProvider DateTimeProvider { get; }
private bool IsDisposing { get; set; }
public async Task Dispose()
{
IsDisposing = true;
while(!IsDisposed)
{
await Task.Delay(50);
}
}
private void UpdateTimeData()
{
TimeText = DateTimeProvider.Now.ToString("HH:mm:ss");
DateText = DateTimeProvider.Now.ToString("dd.MM.yyyy");
}
}

请注意，我也无法从

(HeaderViewModel)weakReference.Target

一旦我这样做了，似乎发生了一些魔法，该实例将再次被捕获。

Answer 2

您的 Dispose 任务似乎永远不会返回，这就是您的对象保留在内存中的原因。我将问题追踪到

await Task.Delay(1000)

如果您根据这篇文章更改它 https://stackoverflow.com/a/24539937/3084003 它将起作用

await Task.Delay(1000).ConfigureAwait(false);