WPF One Way绑定已损坏

Question

我试图将2个不同的WPF控件绑定到ViewModel中的相同属性,一个CheckBox.IsChecked和一个Expander.IsExpanded.我想要实现的行为是让CheckBox影响ViewModel(因此也影响Expander),但不影响其他方式.就像是:

Checkbox Checked -> ViewModel property set to frue -> Expander.Expand
Checkbox Unchecked -> ViewModel property set to false -> Expander.Collapse
Expander Expanded -> Nothing else affected
Expander Collapsed -> Nothing else affected

这是XAML:

<Window x:Class="WpfApplication9.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Expander IsExpanded="{Binding IsChecked, Mode=OneWay}">
        <Expander.Header>
            <CheckBox IsChecked="{Binding IsChecked}" Content="Is Checked"/>
        </Expander.Header>
        <TextBlock Text="Expanded!"/>
    </Expander>
</Window>

和守则:

using System.ComponentModel;
using System.Windows;

namespace WpfApplication9
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            DataContext = new ViewModel();
        }
    }

    public class ViewModel: INotifyPropertyChanged
    {
        private bool _isChecked;
        public bool IsChecked
        {
            get { return _isChecked; }
            set
            {
                _isChecked = value;
                NotifyPropertyChange("IsChecked");
            }
        }

        protected void NotifyPropertyChange(string PropertyName)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(PropertyName));
        }

        public event PropertyChangedEventHandler PropertyChanged = delegate { };
    }
}

现在我的问题是,只要我点击Expander展开/折叠它,Binding就会停止工作.任何人都可以向我解释为什么会发生这种情况,我该如何实现这一目标？提前致谢!

Answer 1

新答案

发现你可以通过设置你这样做UpdateSourceTrigger对Explicit你的扩展.这使绑定保持为双向,但永远不会更新源,因为除非您明确告诉它,否则不要更新源.

<Expander IsExpanded="{Binding IsChecked, UpdateSourceTrigger=Explicit}">
    <Expander.Header>
        <CheckBox IsChecked="{Binding IsChecked}" Content="Is Checked"/>
    </Expander.Header>
    <TextBlock Text="Expanded!"/>
</Expander>

留下我的旧答案,以便评论有意义,因为我仍然觉得视图特定代码在视图的代码隐藏中没有问题:)

老答案

就个人而言,这是特定于视图的代码,我发现使用CheckBox点击事件设置Expander的IsExpanded值没有问题.

private void MyCheckBox_Click(object sender, RoutedEventArgs e)
{
    MyExpander.IsExpanded = ((CheckBox)sender).IsChecked.GetValueOrDefault();
}

您可以通过删除名称并导航Visual Tree来查找与CheckBox关联的Expander来使其更加通用.这是使用我构建的一些Visual Tree Helpers的示例

private void CheckBox_Click(object sender, RoutedEventArgs e)
{
    var chk = (CheckBox)sender;
    var expander = VisualTreeHelpers.FindAncestor<Expander>(chk);

    if (expander != null)
        expander.IsExpanded = chk.IsChecked.GetValueOrDefault();
}