不能理解INotifyPropertyChanged的实现

Question

我只是C＃中的一个新手，我在MSDN博客上阅读INotifyPropertyChanged Event Handler并在这里搜索“stackoverflow”。但我真的不明白如何在代码中实现它，以及如何将事件和属性绑定在一起。

我已经与INotifyPropertyChanged取得了BindingClass，代码为：

namespace Testing.Pages 
{ 
    class BindingClass : INotifyPropertyChanged 
    { 
    private string _setting; 
    public event PropertyChangedEventHandler PropertyChanged; 

    public BindingClass() 
    { 

    } 

    public BindingClass(string value) 
    { 
     _setting = value; 
    } 

    public string SettingProperty 
    { 
     get { return _setting; } 
     set 
     { 
      _setting = value; 
      // calling OnPropertyChanged whenever the property gets updated 

     } 
    } 

    protected void OnPropertyChanged([CallerMemberName] string _setting = "") 
    { 
     PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(_setting)); 
    } 
    } 
} 

SettingsPage.xaml

<TextBlock x:Name="PopupText" 
       Grid.Row="0" 
       HorizontalAlignment="Center" 
       VerticalAlignment="Center" 
       Margin="0,0,0,20" 
       Text="Your theme will be updated next time you start the app." 
       TextWrapping="Wrap" 
       Visibility="Collapsed"> 
     <TextBlock.Resources> 
      <Storyboard x:Name="popup_animate"> 
       <DoubleAnimation Duration="0:0:2" 
           Storyboard.TargetName="PopupText" 
           AutoReverse="True" 
           From="0.0" 
           To="1.0" 
           BeginTime="{x:Bind }" 
           Storyboard.TargetProperty="(TextBlock.Opacity)" 
         ></DoubleAnimation> 
      </Storyboard> 
     </TextBlock.Resources> 
    </TextBlock> 
<TextBlock Text="Change Theme?" 
        Margin="10,10,0,0"></TextBlock> 
     <RadioButton x:Name="DarkTheme_btn" 
        Click="ChangeTheme_btn_Click" 
        Content="Dark Theme" 
        Margin="10,0,0,0" 
        GroupName="theme"></RadioButton> 
     <RadioButton x:Name="LightTheme_btn" 
        Click="ChangeTheme_btn_Click" 
        Content="Light Theme" 
        Margin="10,0,0,0" 
        GroupName="theme"></RadioButton> 

和代码隐藏文件SettingsPage.xaml.cs是：

namespace Testing.Pages 
{ 

/// <summary> 
/// An empty page that can be used on its own or navigated to within a Frame. 
/// </summary> 
    public sealed partial class SettingsPage : Page 
    { 
    BindingClass notifyProperty = new BindingClass(); 

    public SettingsPage() 
    { 
     this.InitializeComponent(); 
     NavigationCacheMode = NavigationCacheMode.Enabled; 
    } 

    private void ChangeTheme_btn_Click(object sender, RoutedEventArgs e) 
    { 
     DataContext = notifyProperty; 
     int notifySettings = 0; 
     if ((bool)DarkTheme_btn.IsChecked) 
     { 
      notifySettings = 2; 
      AppSettings.saveThemeSettings(notifySettings); 
      PopupText.Visibility = Visibility.Visible; 
      popup_animate.Begin(); 
     } 
     else if ((bool)LightTheme_btn.IsChecked) 
     { 
      notifySettings = 1; 
      AppSettings.saveThemeSettings(notifySettings); 
      PopupText.Visibility = Visibility.Visible; 
      popup_animate.Begin(); 
     } 
    } 
    } 
} 

我已经使用了int notifySettings改变LocalSettingsFolder应用程序的设置和应用程序每次重新启动在App.xaml加载设置。每当我更改设置时，我都会调用另一个class中的功能，并且它会更改设置，当我单击SettingsPage.xaml中的这两个radiobuttons中的一个时，将播放animation。这是旧的方法。
现在我想将这些事件绑定在一起，这样我就不必使用int notifySettings和PopupText动画，因为它在每次更新Theme Settings时都会播放。这是我如何也可以了解INotifyPropertyChanged Event。
int notifySettings通过一个int值来相应地更改设置。 1 = LightTheme和2 = DarkTheme。

这里是Settings Class：

namespace Testing.Pages 
{ 
    class AppSettings 
    { 
    public static void saveThemeSettings(int value) 
    { 
     ApplicationDataContainer themeSettings = ApplicationData.Current.LocalSettings; 
     StorageFolder localFolder = ApplicationData.Current.LocalFolder; 
     themeSettings.Values["AppThemeSetting"] = value.ToString(); 
    } 

    public static string readThemeSettings() 
    { 
     ApplicationDataContainer localSettings = ApplicationData.Current.LocalSettings; 
     StorageFolder localFolder = ApplicationData.Current.LocalFolder; 
     string appSettingsString = "error, nothing found"; 
     if (localSettings.Values.ContainsKey("AppThemeSetting")) 
     { 
      appSettingsString = localSettings.Values["AppThemeSetting"]?.ToString(); 
     } 
     return appSettingsString; 
    } 

    public static void removeLocalSettings(string settingValue) 
    { 
     ApplicationData.Current.LocalSettings.Values.Remove(settingValue); 
    } 

    } 

} 

如果仍然有任何含糊之处，请让我知道，我可以尝试进一步解释。我希望有人能帮助我。

更新：
我根据答案由丹尼Bogers但需要Animation不启动，我认为这是因为该功能甚至不被称为修改了自己的项目。我做了一些更改并尝试自行完成，但并没有真正实现，所以我将使用自己的方法来进行更改，直到其他人提出解决方案。

Answer 1

的的PropertyChanged需要知道哪些属性更改，所以你必须通过它的名字。

使它看起来像这样：

public string SettingProperty 
{ 
    get { return _setting; } 
    set 
    { 
     if(_setting != value) // Or String.Equals(_setting, value, ...) 
     { 
      _setting = value; 
      OnPropertyChanged(); // Invoke using no argument. 
     } 
    } 
} 

protected void OnPropertyChanged([CallerMemberName] string propertyName = "") 
{ 
    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)); 
} 

的OnPropertyChanged方法使用它的参数CallerMemberName属性，该属性也是可选的。这意味着编译器将使用这个参数并将iith替换为调用者的实际名称。所以不要自己传递任何价值。

它相当于PropertyChanged("SettingProperty")。然而属性使折射器安全。

关于你的问题的其余部分：我相信这个问题本身带来太多问题，并且包含至少一个以上的问题。所以一旦你修复了属性改变的部分，而是问了一个具体问题的新问题。

Answer 2

我不是最擅长解释的东西，我希望你能得到它的要点！ 我也没有时间来正确地测试它，但是这应该可以完成这项工作。

您可以通过+=语法订阅事件。现在，无论何时提出事件，所有订户都会被解雇。在这种情况下，一个PropertyChangedEventArgs的实例。这允许您的订户根据给定的EventArgs的值而行为不同（您也可以将EventArgs的空实例传递给您的订户，这意味着您的订户不会根据EventArgs中的值进行任何操作）。

一些细微的变化：

• 增加了对主题的枚举。检查选择哪个主题时添加类型安全性。这比检查硬编码字符串要好。

• 无法找到ThemeSetting时添加了异常。您可以在try/catch块中相应地处理异常。这再次比检查硬编码字符串更好。

• 为您的应用程序密钥添加了一个常量字符串。与前面两点一样，这将防止由于错字造成的运行时错误/为您提供一个集中位置来管理值。

  namespace Testing.Pages 
  { 
      public enum Themes 
      { 
       Light = 1, 
       Dark = 2 
      } 
  } 
  
  namespace Testing.Pages 
  { 
      public class ThemeSettingNotFoundException : Exception 
      { 
       public ThemeSettingNotFoundException() : base("error, nothing found") 
       { 
       } 
      } 
  
  } 
  
  namespace Testing.Pages 
  { 
      class BindingClass : INotifyPropertyChanged 
      { 
       private string _setting; 
       public event PropertyChangedEventHandler PropertyChanged; 
  
       public BindingClass() { 
  
       } 
  
       public BindingClass(string value) { 
        _setting = value; 
       } 
  
       public string SettingProperty 
       { 
        get { return _setting; } 
        set 
        { 
         if(!_setting.Equals(value)){ 
          _setting = value; 
          OnPropertyChanged(); 
         } 
        } 
       } 
  
       protected void OnPropertyChanged([CallerMemberName] string _setting = "") { 
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(_setting)); 
       } 
      } 
  } 
  
  
  namespace Testing.Pages 
  { 
  
      /// <summary> 
      /// An empty page that can be used on its own or navigated to within a Frame. 
      /// </summary> 
      public sealed partial class SettingsPage : Page 
      { 
       BindingClass notifyProperty = new BindingClass(); 
  
       public SettingsPage() { 
        this.InitializeComponent(); 
        NavigationCacheMode = NavigationCacheMode.Enabled; 
  
        //Subscribe to the PropertyChanged event 
        notifyProperty.PropertyChanged += OnThemeSettingChanged; 
       } 
  
       private void ChangeTheme_btn_Click(object sender, RoutedEventArgs e) { 
        DataContext = notifyProperty; 
        SaveThemeSettings(); 
       } 
  
       private void SaveThemeSettings() 
       { 
        var notifySettings = 0; 
        if ((bool)DarkTheme_btn.IsChecked) 
         notifySettings = 2; 
        else if ((bool)LightTheme_btn.IsChecked) 
         notifySettings = 1; 
  
        //Only save theme settings when a button was checked 
        if (notifySettings != 0) 
         AppSettings.saveThemeSettings((Themes)notifySettings); 
       } 
  
       private void OnThemeSettingChanged(object sender, PropertyChangedEventArgs args) 
       { 
        PopupText.Visibility = Visibility.Visible; 
        popup_animate.Begin(); 
       } 
      } 
  } 
  
  
  namespace Testing.Pages 
  { 
      class AppSettings 
      { 
       private const string ThemeSettingKey = "AppThemeSetting"; 
  
       public static void saveThemeSettings(Themes theme) { 
        ApplicationDataContainer themeSettings = ApplicationData.Current.LocalSettings; 
        themeSettings.Values[ThemeSettingKey] = theme.ToString(); 
       } 
  
       public static Themes readThemeSettings() { 
        ApplicationDataContainer localSettings = ApplicationData.Current.LocalSettings; 
        if (!localSettings.Values.ContainsKey(ThemeSettingKey)) 
         throw new ThemeSettingNotFoundException(); 
        var appSettingsString = localSettings.Values[ThemeSettingKey]; 
        return (Themes)Enum.Parse(typeof(Themes), appSettingsString); 
       } 
  
       public static void removeLocalSettings(string settingValue) { 
        ApplicationData.Current.LocalSettings.Values.Remove(settingValue); 
       } 
      } 
  }