了解 WPF 中提供的 DispatcherPriority 枚举的真实行为
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原文地址: http://stackoverflow.com/questions/33701510/
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Understanding the true behavior of the DispatcherPriority enum provided in WPF
提问by William
There is documentation with definitions on what each enum does. But how am I able to demo/see this in practice? And how can I possibly know when to use which priority?
有文档定义了每个枚举的作用。但是我如何能够在实践中演示/看到这一点？我怎么可能知道什么时候使用哪个优先级？
Here's some code I have created in attempt to see how the priorty affects the ordering, and it provides me with proof that the ordering is correct (the first loop iteration will have added a SystemIdle enum to the dispatch queue), but it still got added to the string last
这是我创建的一些代码，试图查看优先级如何影响排序，它为我提供了排序正确的证据（第一次循环迭代将 SystemIdle 枚举添加到调度队列），但它仍然被添加最后到字符串
private void btn_Click(object sender, RoutedEventArgs e)
{
StringBuilder result = new StringBuilder();
new Thread(() =>
{
var vals = Enum.GetValues(typeof(DispatcherPriority)).Cast<DispatcherPriority>().Where(y => y >= 0).ToList();
vals.Reverse();
vals.ForEach(x =>
{
Dispatcher.BeginInvoke(new Action(() =>
{
result.AppendLine(string.Format("Priority: {0} Enum:{1}", ((int)x), x.ToString()));
}), x);
});
}).Start();
ShowResultAsync(result, 2000);
}
private async void ShowResultAsync(StringBuilder s, int delay)
{
await Task.Delay(delay);
MessageBox.Show(s.ToString());
}
and the output order stays the same, even when the list is reversed (added this line just after valsgets assigned):
并且输出顺序保持不变，即使列表颠倒了（在vals分配之后添加了这一行）：
vals.Reverse();
So once again, is there anything more I can use when determining which dispatch priority I should assign?
那么再一次，在确定我应该分配哪个调度优先级时，还有什么我可以使用的吗？
采纳答案by Ethan Cabiac
In the Prism Frameworkthe DefaultDispatcherwhich wraps Dispatcheruses a Normalpriority. This should be the bread-and-butter for nearly all application scenarios.
在Prism 框架中，DefaultDispatcherwhich wrapsDispatcher使用Normal优先级。这应该是几乎所有应用场景的基本要素。
/// <summary>
/// Wraps the Application Dispatcher.
/// </summary>
public class DefaultDispatcher : IDispatcherFacade
{
/// <summary>
/// Forwards the BeginInvoke to the current application's <see cref="Dispatcher"/>.
/// </summary>
/// <param name="method">Method to be invoked.</param>
/// <param name="arg">Arguments to pass to the invoked method.</param>
public void BeginInvoke(Delegate method, object arg)
{
if (Application.Current != null)
{
Application.Current.Dispatcher.BeginInvoke(DispatcherPriority.Normal, method, arg);
}
}
}
As long as you are not running any actual logic on the UI thread I would recommend doing this.
只要您不在 UI 线程上运行任何实际逻辑，我就会建议您这样做。
If you did for some reason want to run "quick" logic on the UI thread you could follow the advice hereand stick with a value of Background.
如果您出于某种原因想要在 UI 线程上运行“快速”逻辑，您可以遵循此处的建议并坚持使用Background.
I did look into it a little and I found some usages in NuGet's sourcewhere they use Send, Normal, Backgroundand ApplicationIdlefor various reasons but in my WPF development I have never had to fine tune usage of DispatcherPriorityto this degree.
我没有看进去一点，我发现在一些使用的NuGet的来源，他们使用Send，Normal，Background和ApplicationIdle由于各种原因，但在我的WPF发展我从未有过的微调使用DispatcherPriority到这种程度。
