WPF数据绑定马歇尔是否更改为UI线程？ [英] Does WPF databinding marshall changes to the UI Thread?

问题描述

我刚刚注意到，从后台工作线程中更改我的 ViewModel （MVVM）中的绑定属性时，我没有得到任何异常，视图被正确更新。这是否意味着我可以安全地依靠wpf数据绑定将 ViewModel 中的所有更改编组到UI线程？我想我已经读过某个地方应该确定（在 ViewModel 中）， INotifyPropertyChanged.PropertyChanged 在UI线程。这个变化是在3.5还是什么？

I just noticed that when changing bound properties in my ViewModel (MVVM) from a background worker thread I do not get any exceptions and the view is updated correctly. Does this mean I can safely rely on wpf databinding marshalling all changes in the ViewModel to the UI Thread? I think I have read somewhere that one should make sure (in the ViewModel) that INotifyPropertyChanged.PropertyChanged is fired on the UI thread. Has this changed in 3.5 or something?

推荐答案

是标量，是否为集合。对于集合，您需要一个为您编排的专门的集合，或者通过调度程序自己手动组织UI线程。

Yes for scalars, no for collections. For collections, you'll need a specialized collection that marshals for you, or manually marshal to the UI thread yourself via the Dispatcher.

您可能已经阅读了 INotifyCollectionChanged.CollectionChanged 必须在UI线程上触发，因为 INotifyPropertyChanged.PropertyChanged 。以下是一个非常简单的例子，它为您证明了WPF marshals属性更改。

You may have read that INotifyCollectionChanged.CollectionChanged must fire on the UI thread, because it's simply not true of INotifyPropertyChanged.PropertyChanged. Below is a very simple example that proves WPF marshals property changes for you.

Window1.xaml.cs ：

using System.ComponentModel;
using System.Threading;
using System.Windows;

namespace WpfApplication1
{
    public partial class Window1 : Window
    {
        private CustomerViewModel _customerViewModel;

        public Window1()
        {
            InitializeComponent();
            _customerViewModel = new CustomerViewModel();
            DataContext = _customerViewModel;

            var thread = new Thread((ThreadStart)delegate
            {
                while (true)
                {
                    Thread.Sleep(2000);
                    //look ma - no marshalling!
                    _customerViewModel.Name += "Appended";
                    _customerViewModel.Address.Line1 += "Appended";
                }
            });

            thread.Start();
        }
    }

    public abstract class ViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        protected void OnPropertyChanged(string propertyName)
        {
            var handler = PropertyChanged;

            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }

    public class CustomerViewModel : ViewModel
    {
        private string _name;
        private AddressViewModel _address = new AddressViewModel();

        public string Name
        {
            get { return _name; }
            set
            {
                if (_name != value)
                {
                    _name = value;
                    OnPropertyChanged("Name");
                }
            }
        }

        public AddressViewModel Address
        {
            get { return _address; }
        }
    }

    public class AddressViewModel : ViewModel
    {
        private string _line1;

        public string Line1
        {
            get { return _line1; }
            set
            {
                if (_line1 != value)
                {
                    _line1 = value;
                    OnPropertyChanged("Line1");
                }
            }
        }
    }
}

Window1.xaml ：

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <StackPanel>
        <TextBox Text="{Binding Name}"/>
        <TextBox Text="{Binding Address.Line1}"/>
    </StackPanel>
</Window>

这篇关于WPF数据绑定马歇尔是否更改为UI线程？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！