RelativeSource绑定工具提示到UserControl依赖属性错误

Question

我有一个自定义usercontrol，它在DispatcherTimer滴答上做一个小动画，以及更新usercontrol的DependencyProperty:

public partial class EggCounter : UserControl
{
  DispatcherTimer eggTimer;
  public EggCounter()
  {
     // Required to initialize variables
     InitializeComponent();
     eggTimer = new DispatcherTimer();
     eggTimer.Interval = TimeSpan.FromSeconds(5);
     eggTimer.Tick += new EventHandler(eggTimer_Tick);
     eggTimer.Start();
     Eggs = 0;
  }
  void eggTimer_Tick(object sender, EventArgs e)
  {
     Eggs += 4;
     Pop.Begin();
     mePop.Play();
  }
  private void mePop_MediaEnded(object sender, RoutedEventArgs e)
  {
     mePop.Position = TimeSpan.FromSeconds(0);
  }
  /// <summary>
  /// The <see cref="Eggs" /> dependency property's name.
  /// </summary>
  public const string EggsPropertyName = "Eggs";
  /// <summary>
  /// Gets or sets the value of the <see cref="Eggs" />
  /// property. This is a dependency property.
  /// </summary>
  public int Eggs
  {
     get
     {
        return (int)GetValue(EggsProperty);
     }
     set
     {
        SetValue(EggsProperty, value);
     }
  }
  /// <summary>
  /// Identifies the <see cref="Eggs" /> dependency property.
  /// </summary>
  public static readonly DependencyProperty EggsProperty = DependencyProperty.Register(EggsPropertyName, typeof(int), typeof(EggCounter), new UIPropertyMetadata(0));
}

此代码的XAML无关紧要。然后，我将这个控件放在MainPage上，如下所示:

<my:EggCounter ToolTipService.ToolTip="{Binding RelativeSource={RelativeSource Self}, Path=Eggs, StringFormat='{} Our chickens have laid {0} eggs since you have been here.'}"/>

页面加载正常，但一旦计时器触发，我得到这个错误:

"The given key was not present in the dictionary."

在我的usercontrol中的Eggs属性的setter中，即在这一行:

SetValue(EggsProperty, value);

我也尝试在控件上使用ElementBinding，但得到相同的错误。我做了什么错误的依赖属性?

Answer 1

您的代码中包含UIPropertyMetaData。Silverlight没有这个类，它只使用PropertyMetaData代替。

我已经说过你描述的失败模式似乎表明你的代码可以编译，我不明白是怎么做到的。

Answer 2

如果使用您的代码，我不会得到错误。

但是我没有

Pop.Begin();
mePop.Play();

在TimerCallback中。所以也许你应该在这两个方法中寻找错误。