c# - 为什么 WPF 中的 UI 控件具有线程亲和性？

Question

为什么创建控件的线程是可以更新它的线程？为什么 MS 没有让人们能够使用锁定和其他线程同步技术来读取和写入具有多线程的 UI 控件上的属性。

Answer 1

每个 MSDN 的简短描述是

WPF’s threading model was kept in sync with the existing User32 threading model of single threaded execution with thread affinity. The primary reason for this was interoperability – systems like OLE 2.0, the clipboard, and Internet Explorer all require single thread affinity (STA) execution

较长的描述是这样的:

Most objects in WPF derive from DispatcherObject, which provides the basic constructs for dealing with concurrency and threading. WPF is based on a messaging system implemented by the dispatcher. This works much like the familiar Win32 message pump; in fact, the WPF dispatcher uses User32 messages for performing cross thread calls.

There are really two core concepts to understand when discussing concurrency in WPF – the dispatcher and thread affinity.

During the design phase of WPF, the goal was to move to a single thread of execution, but a non-thread "affinitized" model. Thread affinity happens when a component uses the identity of the executing thread to store some type of state. The most common form of this is to use the thread local store (TLS) to store state. Thread affinity requires that each logical thread of execution be owned by only one physical thread in the operating system, which can become memory intensive. In the end, WPF’s threading model was kept in sync with the existing User32 threading model of single threaded execution with thread affinity. The primary reason for this was interoperability – systems like OLE 2.0, the clipboard, and Internet Explorer all require single thread affinity (STA) execution.

Given that you have objects with STA threading, you need a way to communicate between threads, and validate that you are on the correct thread. Herein lies the role of the dispatcher. The dispatcher is a basic message dispatching system, with multiple prioritized queues. Examples of messages include raw input notifications (mouse moved), framework functions (layout), or user commands (execute this method). By deriving from DispatcherObject, you create a CLR object that has STA behavior, and will be given a pointer to a dispatcher at creation time.

您可以阅读全文 here

我个人更喜欢 WPF 的单线程模型，而不是必须使用锁定和线程同步技术。 Dispatcher可用于将消息传递到位于 different priority levels 的主 UI 线程，它负责处理大部分小型后台进程，如果您需要任何繁重的处理，您仍然可以为此创建自己的后台线程。