C# 线程安全(特别是 MVVM/WPF) [英] C# thread safety (in particular MVVM/WPF)

问题描述

我想知道我需要做什么才能使 MVVM 中的模型线程安全.假设我有以下类，它被实例化为单例:

I'm wondering what I need to do to make models thread safe in MVVM. Say I had the following class, which is instantiated as a singleton:

public class RunningTotal: INotifyPropertyChange
{
   private int _total;
   public int Total
   {
      get { return _total; }
      set
      {
         _total = value;
         PropertyChanged("Total");
      }
   }
   ...etc...
}

我的视图模型通过属性公开它:

My view model exposes it via a property:

public RunningTotal RunningTotal { get; }

我的视图绑定了一个文本块，即{Binding Path=RunningTotal.Total}.

And my view has a textblock bound to it, i.e. {Binding Path=RunningTotal.Total}.

我的应用程序有一个后台线程，它会定期更新 Total 的值.假设没有其他东西更新 Total，我应该怎么做(如果有的话)才能使所有这些线程安全?

My app has a background thread that periodically updates the value of Total. Assuming nothing else updates Total, what (if anything) should I do to make all this thread-safe?

现在，如果我想做类似的事情，但使用 Dictionary<> 或 ObservableCollection<> 类型的属性怎么办?哪些成员(添加、删除、清除、索引器)是线程安全的?我应该改用 ConcurrentDictionary 吗?

Now, what if I wanted to do something similar but using a property of type Dictionary<>, or ObservableCollection<>? Which members (add, remove, clear, indexer) are thread-safe? Should I use a ConcurrentDictionary instead?

推荐答案

我的应用程序有一个后台线程，它会定期更新 Total 的值.假设没有其他东西更新 Total，我应该怎么做(如果有的话)才能使所有这些线程安全?

My app has a background thread that periodically updates the value of Total. Assuming nothing else updates Total, what (if anything) should I do to make all this thread-safe?

对于标量属性，你不需要做任何特别的事情；PropertyChanged 事件会自动编组到 UI 线程.

For scalar properties, you don't need to do anything special; the PropertyChanged event is automatically marshaled to the UI thread.

现在，如果我想做类似的事情但使用类型为 Dictionary<> 或 ObservableCollection<> 的属性怎么办?哪些成员(添加、删除、清除、索引器)是线程安全的?我应该改用 ConcurrentDictionary 吗?

Now, what if I wanted to do something similar but using a property of type Dictionary<>, or ObservableCollection<>? Which members (add, remove, clear, indexer) are thread-safe? Should I use a ConcurrentDictionary instead?

不，这不是线程安全的.如果您从后台线程更改 ObservableCollection 的内容，它将中断.您需要在 UI 线程上执行此操作.一种简单的方法是使用一个在 UI 线程上引发其事件的集合，例如 此处.

No, this is not thread-safe. If you change the content of an ObservableCollection<T> from a background thread, it will break. You need to do it on the UI thread. An easy way to do it is to use a collection that raises its events on the UI thread, like the one described here.

至于Dictionary，当它的内容发生变化时，它不会发出通知，因此无论如何也不会通知UI.

As for Dictionary<TKey, TValue>, it doesn't raise a notification when its content changes, so the UI is not notified anyway.

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