Question

我有一个字符串依赖属性（SearchText），更新后需要更新集合依赖属性（Results）。
我的收藏dp：

public IEnumerable<string> Results{
  get { return (IEnumerable<string>) GetValue(ResultsProperty); }
  set { SetValue(ResultsProperty, value); }
}
public static readonly DependencyProperty ResultsProperty= 
DependencyProperty.Register("Results", typeof(IEnumerable<string>), typeof(MainWindowVM), new UIPropertyMetadata(new List<string>()));

我试了这个没有运气。我在结果= ....线上放了一个断点，它从未被击中。

public string SearchText{
  get { return (string) GetValue(SearchTextProperty); }
  set {
    Results =
          from T in Tree.GetPeople(value)
          select T.FullName;
    SetValue(SearchTextProperty, value);
  }
}
public static readonly DependencyProperty SearchTextProperty= 
DependencyProperty.Register("SearchText", typeof(string), typeof(MainWindowVM), new UIPropertyMetadata(""));

XAML：

<TextBox DockPanel.Dock="Top" Text="{Binding SearchValue, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />

<ListBox DockPanel.Dock="Top" ItemsSource="{Binding NameResults}" SelectedItem="{Binding Search}" />

Answer 1

在XAML中设置依赖项属性或通过绑定时，运行时将始终绕过实例属性别名，并直接调用GetValue和SetValue。正因为如此，您的实例设置器才被调用。

您可能希望考虑的是使用依赖项属性注册方法，该属性将在属性更改时调用。在为依赖项属性创建PropertyMetadata时，这很容易完成。

我相信以下示例会执行您要执行的操作。在该示例中，我的类具有两个依赖属性别名为First和Second。当我为First设置值时，我的变更处理程序被调用，我将值设置为Second。

public class DependencyPropertyTest : DependencyObject
{
  public static readonly DependencyProperty FirstProperty;
  public static readonly DependencyProperty SecondProperty;

  static DependencyPropertyTest()
  {
    FirstProperty  = DependencyProperty.Register("FirstProperty", 
                                                  typeof(bool), 
                                                  typeof(DependencyPropertyTest), 
                                                  new PropertyMetadata(false, FirstPropertyChanged));

    SecondProperty = DependencyProperty.Register("SecondProperty", 
                                                 typeof(string), 
                                                 typeof(DependencyPropertyTest), 
                                                 new PropertyMetadata(null));
  } // End constructor

  private bool First
  {
    get { return (bool)this.GetValue(FirstProperty); }
    set { this.SetValue(FirstProperty, value);       }

  } // End property First

  private string Second
  {
    get { return (string)this.GetValue(SecondProperty); }
    set { this.SetValue(SecondProperty, value);         }

  } // End property Second

  private static void FirstPropertyChanged(DependencyObject dependencyObject, 
                                           DependencyPropertyChangedEventArgs ea)
  {
    DependencyPropertyTest instance = dependencyObject as DependencyPropertyTest;

    if (instance == null)
    {
      return;
    }

    instance.Second = String.Format("First is {0}.", ((bool)ea.NewValue).ToString());

  } // End method FirstPropertyChanged
} // End class DependencyPropertyTest

我希望有所帮助。

Answer 2

正如我评论的那样，当前接受的答案在原则上是正确的，除了它必须使用SetCurrentValue方法而不是做一个简单的赋值。有关它的更多说明，请参阅this answer。

以下是与此修复程序相同的代码：

public class DependencyPropertyTest : DependencyObject
{
  public static readonly DependencyProperty FirstProperty;
  public static readonly DependencyProperty SecondProperty;

  static DependencyPropertyTest()
  {
    FirstProperty  = DependencyProperty.Register("FirstProperty", 
                                                  typeof(bool), 
                                                  typeof(DependencyPropertyTest), 
                                                  new PropertyMetadata(false, FirstPropertyChanged));

    SecondProperty = DependencyProperty.Register("SecondProperty", 
                                                 typeof(string), 
                                                 typeof(DependencyPropertyTest), 
                                                 new PropertyMetadata(null));
  } // End constructor

  private bool First
  {
    get { return (bool)this.GetValue(FirstProperty); }
    set { this.SetValue(FirstProperty, value);       }

  } // End property First

  private string Second
  {
    get { return (string)this.GetValue(SecondProperty); }
    set { this.SetValue(SecondProperty, value);         }

  } // End property Second

  private static void FirstPropertyChanged(DependencyObject dependencyObject, 
                                           DependencyPropertyChangedEventArgs ea)
  {
    DependencyPropertyTest instance = dependencyObject as DependencyPropertyTest;

    if (instance == null)
    {
      return;
    }

    // SetCurrentValue should be used here!
    instance.SetCurrentValue(SecondProperty,
      String.Format("First is {0}.", ((bool)ea.NewValue).ToString());

  } // End method FirstPropertyChanged
} // End class DependencyPropertyTest

Answer 3

您在其依赖项属性上放置的顺序非常重要放在类文件中的第一把拳头将被执行，然后再向下一个拳头

class A {
dependecy 1
dependecy 2 
dependecy 3
}

它将按照在类上设置的顺序进行调用，，因此只需对所需顺序进行依赖即可如果1取决于2->首先放置2，则像这样放置1

class A {
dependecy 2 
dependecy 1
dependecy 3
}

从另一个更新一个依赖项属性

3 个答案: