WPF DataBinding不更新？ [英] WPF DataBinding not updating?

问题描述

我有一个项目，我将一个复选框的IsChecked属性与codebehind中的get / set绑定。但是，当应用程序加载时，由于某些原因它不会更新。有趣的是，我把它剥夺了它的基础，像这样：

  //使用语句
命名空间NS 
 {
 ///< summary> 
 /// MainWindow.xaml的交互逻辑
 ///< / summary> 
 public partial class MainWindow：Window 
 {
 private bool _test; 
 public bool Test 
 {
 get {Console.WriteLine（Accessed！）;返回_test; } 
 set {Console.WriteLine（Changed！）; _test = value; } 
} 
 public MainWindow（）
 {
 InitializeComponent（）; 
 Test = true; 
} 
} 
} 
  

XAML：

 < Window x：Class =TheTestingProject_WPF_.MainWindow
 xmlns =http://schemas.microsoft.com/winfx / 2006 / xaml / presentation
 xmlns：x =http://schemas.microsoft.com/winfx/2006/xaml
 Title =MainWindowHeight =350Width =525 DataContext ={Binding RelativeSource = {RelativeSource Self}}> 
< Grid> 
< Viewbox> 
< CheckBox IsChecked ={Binding Path = Test，Mode = TwoWay，UpdateSourceTrigger = PropertyChanged}/> 
< / Viewbox> 
< / Grid> 
  

而且，当我设置为true时，它没有更新！

任何人都可以提出修复，或解释为什么？

谢谢，不胜感激。

解决方案

为了支持双向绑定，您的数据对象必须实施 INotifyPropertyChanged

另外，总是一个好主意，将数据从演示文稿中分离出来

  public class ViewModel：INotifyPropertyChanged 
 {
 private bool _test; 
 public bool Test 
 {get {return _test; } 
 set 
 {
 _test = value; 
 NotifyPropertyChanged（Test）; 
} 
} 
 
 public PropertyChangedEventHandler PropertyChanged; 
 
 public void NotifyPropertyChanged（string propertyName）
 {
 if（PropertyChanged！= null）
 PropertyChanged（this，new PropertyChangedEventArgs（propertyName））; 
} 
} 
 
< Window x：Class =TheTestingProject_WPF_.MainWindow
 xmlns =http://schemas.microsoft.com/winfx/2006 / xaml / presentation
 xmlns：x =http://schemas.microsoft.com/winfx/2006/xaml
 Title =MainWindowHeight =350Width =525> ; 
< Grid> 
< Viewbox> 
< CheckBox IsChecked ={Binding Path = Test，Mode = TwoWay，UpdateSourceTrigger = PropertyChanged}/> 
< / Viewbox> 
< / Grid> 
  

代码背后：

  public partial class MainWindow：Window 
 {
 public MainWindow（）
 {
 InitializeComponent（）; 
 DataContext = new ViewModel {Test = true}; 
} 
} 
  

I have a project, where I bind a checkbox's IsChecked property with a get/set in the codebehind. However, when the application loads, it doesn't update, for some reason. Intrigued, I stripped it down to its basics, like this:

//using statements
namespace NS
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private bool _test;
        public bool Test
        {
            get { Console.WriteLine("Accessed!"); return _test; }
            set { Console.WriteLine("Changed!"); _test = value; }
        }
        public MainWindow()
        {
            InitializeComponent();
            Test = true;
        }
    }
}

XAML:

<Window x:Class="TheTestingProject_WPF_.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" DataContext="{Binding RelativeSource={RelativeSource Self}}">
<Grid>
    <Viewbox>
        <CheckBox IsChecked="{Binding Path=Test, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
    </Viewbox>
</Grid>

And, lo and behold, when I set it to true, it did not update!

Anyone can come up with a fix, or explain why?

Thanks, it'd be appreciated.

解决方案

In order to support two-way binding, your data object must implement INotifyPropertyChanged

Also, it's always a good idea to Separate Data from Presentation

public class ViewModel: INotifyPropertyChanged
{
    private bool _test;
    public bool Test
    {  get { return _test; }
       set
       {
           _test = value;
           NotifyPropertyChanged("Test");
       }
    }

    public PropertyChangedEventHandler PropertyChanged;

    public void NotifyPropertyChanged(string propertyName)
    {
         if (PropertyChanged != null)
             PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

<Window x:Class="TheTestingProject_WPF_.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">
<Grid>
    <Viewbox>
        <CheckBox IsChecked="{Binding Path=Test, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
    </Viewbox>
</Grid>

Code Behind:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        DataContext = new ViewModel{Test = true};
    }
}

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