重新評估UserControl中的屬性

Question

我正在使用C＃-WPF。

我做了我自己的UserControl，一個簡單的十字。通過座標，我可以在圖像上繪製一個X.

參數爲：

• CenterPoint的：中心的橫
• 前景：色爲橫
• 厚度：厚度爲十字

我Cross.xaml：

<UserControl x:Name="userControl" 
      x:Class="Project.Cross"> 
    <Grid> 
     <Line Stroke="{Binding Foreground, ElementName=userControl}" 
       StrokeThickness="{Binding Thickness, ElementName=userControl}" 
       X1="{Binding X1, ElementName=userControl, Mode=OneWay}" 
       X2="{Binding X2, ElementName=userControl, Mode=OneWay}" 
       Y1="{Binding Y1, ElementName=userControl, Mode=OneWay}" 
       Y2="{Binding Y2, ElementName=userControl, Mode=OneWay}" /> 

     <Line Stroke="{Binding Foreground, ElementName=userControl}" 
       StrokeThickness="{Binding Thickness, ElementName=userControl}" 
       X1="{Binding X2, ElementName=userControl, Mode=OneWay}" 
       X2="{Binding X1, ElementName=userControl, Mode=OneWay}" 
       Y1="{Binding Y1, ElementName=userControl, Mode=OneWay}" 
       Y2="{Binding Y2, ElementName=userControl, Mode=OneWay}"/> 
    </Grid> 
</UserControl> 

我Cross.xaml.cs：

public partial class Cross : UserControl 
{ 
    public Cross() 
    { 
     InitializeComponent(); 
    } 

    public readonly static DependencyProperty CenterPointProperty = DependencyProperty.Register("CenterPoint", 
     typeof(PointF), typeof(Cross), 
     new PropertyMetadata(default(PointF))); 

    public PointF CenterPoint 
    { 
     get { return (PointF)GetValue(CenterPointProperty); } 
     set { SetValue(CenterPointProperty, value); } 
    } 

    public readonly static DependencyProperty ThicknessProperty = DependencyProperty.Register("Thickness", 
     typeof(int), typeof(Cross), 
     new PropertyMetadata(2)); 

    public int Thickness 
    { 
     get { return (int)GetValue(ThicknessProperty); } 
     set { SetValue(ThicknessProperty, value); } 
    } 

    public float X1 
    { 
     get 
     { 
      return (float)(CenterPoint.X - (Width/2)); 
     } 
    } 
    public float X2 
    { 
     get 
     { 
      return (float)(CenterPoint.X + (Width/2)); 
     } 
    } 
    public float Y1 
    { 
     get 
     { 
      return (float)(CenterPoint.Y - (Height/2)); 
     } 
    } 
    public float Y2 
    { 
     get 
     { 
      return (float)(CenterPoint.Y + (Height/2)); 
     } 
    } 
} 

我可以把它想：

<local:Cross CenterPoint="{Binding Point}" Thickness="8" Foreground="Yellow" Height="40" Width="40"/> 

我有一個問題，則不會顯示在十字架上。我添加了斷點，看起來X1，X2，...在更改CenterPoint時不會刷新。我如何強制C＃重新評估這些值？ （希望這解決了我的問題）

謝謝

Answer 1

MM8的方法將更新X1等方面的工作，但也有需要解決的另外的問題使控制工作。

我使用的是另一種方式來更新協調性：讓X1等進入read-only dependency properties，和你的用戶控件更新它們的時候CenterPoint變化和當控件的大小變化。

我也改變了你的WinForms PointF到WPF的System.Windows.Point，它使用double爲X和Y，我已經改變了Thickness到float爲好，因爲WPF使用float線路厚度，你不妨充分優點。

我更新的SizeChanged事件，這是至關重要的座標，否則，座標屬性將只在控件創建時的實際大小爲0×0，和Width和Height是NaN設置。

最後，你應該使用ActualWidth和ActualHeight，這是更新的「活」不像Height和Width，這是設計時的屬性值。如果你給它一個固定的Width和Height，效果將是相同的;如果需要的話，使用ActualWidth和ActualHeight可以拉伸以適應容器。

public partial class Cross : UserControl 
{ 
    public Cross() 
    { 
     InitializeComponent(); 

     SizeChanged += Cross_SizeChanged; 
    } 

    private void Cross_SizeChanged(object sender, SizeChangedEventArgs e) 
    { 
     UpdateXYProperties(); 
    } 

    protected void UpdateXYProperties() 
    { 
     X1 = (float)(CenterPoint.X - (ActualWidth/2)); 
     X2 = (float)(CenterPoint.X + (ActualWidth/2)); 
     Y1 = (float)(CenterPoint.Y - (ActualHeight/2)); 
     Y2 = (float)(CenterPoint.Y + (ActualHeight/2)); 
    } 

    public readonly static DependencyProperty CenterPointProperty = DependencyProperty.Register(nameof(CenterPoint), 
     typeof(Point), typeof(Cross), 
     new PropertyMetadata(default(Point), CenterPoint_PropertyChanged)); 

    private static void CenterPoint_PropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e) 
    { 
     ((Cross)obj).UpdateXYProperties(); 
    } 

    public Point CenterPoint 
    { 
     get { return (Point)GetValue(CenterPointProperty); } 
     set { SetValue(CenterPointProperty, value); } 
    } 

    public readonly static DependencyProperty ThicknessProperty = DependencyProperty.Register(nameof(Thickness), 
     typeof(float), typeof(Cross), 
     new PropertyMetadata(2.0F)); 

    public float Thickness 
    { 
     get { return (float)GetValue(ThicknessProperty); } 
     set { SetValue(ThicknessProperty, value); } 
    } 

    #region Read-Only Properties 
    #region X1 Property 
    public float X1 
    { 
     get { return (float)GetValue(X1Property); } 
     protected set { SetValue(X1PropertyKey, value); } 
    } 

    internal static readonly DependencyPropertyKey X1PropertyKey = 
     DependencyProperty.RegisterReadOnly("X1", typeof(float), typeof(Cross), 
      new PropertyMetadata(0.0F)); 

    public static readonly DependencyProperty X1Property = X1PropertyKey.DependencyProperty; 
    #endregion X1 Property 

    #region X2 Property 
    public float X2 
    { 
     get { return (float)GetValue(X2Property); } 
     protected set { SetValue(X2PropertyKey, value); } 
    } 

    internal static readonly DependencyPropertyKey X2PropertyKey = 
     DependencyProperty.RegisterReadOnly("X2", typeof(float), typeof(Cross), 
      new PropertyMetadata(0.0F)); 

    public static readonly DependencyProperty X2Property = X2PropertyKey.DependencyProperty; 
    #endregion X2 Property 

    #region Y1 Property 
    public float Y1 
    { 
     get { return (float)GetValue(Y1Property); } 
     protected set { SetValue(Y1PropertyKey, value); } 
    } 

    internal static readonly DependencyPropertyKey Y1PropertyKey = 
     DependencyProperty.RegisterReadOnly("Y1", typeof(float), typeof(Cross), 
      new PropertyMetadata(0.0F)); 

    public static readonly DependencyProperty Y1Property = Y1PropertyKey.DependencyProperty; 
    #endregion Y1 Property 

    #region Y2 Property 
    public float Y2 
    { 
     get { return (float)GetValue(Y2Property); } 
     protected set { SetValue(Y2PropertyKey, value); } 
    } 

    internal static readonly DependencyPropertyKey Y2PropertyKey = 
     DependencyProperty.RegisterReadOnly("Y2", typeof(float), typeof(Cross), 
      new PropertyMetadata(0.0F)); 

    public static readonly DependencyProperty Y2Property = Y2PropertyKey.DependencyProperty; 
    #endregion Y2 Property 
    #endregion Read-Only Properties 
} 

最後，你並不需要明確地讓你的綁定Mode=OneWay，因爲Line.X1等無法更新綁定源（那是你自己的X1等。在這種情況下），所以他們已經默認爲OneWay。

<Grid> 
    <Line 
     Stroke="{Binding Foreground, ElementName=userControl}" 
     StrokeThickness="{Binding Thickness, ElementName=userControl}" 
     X1="{Binding X1, ElementName=userControl}" 
     X2="{Binding X2, ElementName=userControl}" 
     Y1="{Binding Y1, ElementName=userControl}" 
     Y2="{Binding Y2, ElementName=userControl}" 
     /> 

    <Line 
     Stroke="{Binding Foreground, ElementName=userControl}" 
     StrokeThickness="{Binding Thickness, ElementName=userControl}" 
     X1="{Binding X2, ElementName=userControl}" 
     X2="{Binding X1, ElementName=userControl}" 
     Y1="{Binding Y1, ElementName=userControl}" 
     Y2="{Binding Y2, ElementName=userControl}" 
     /> 
</Grid> 

最後，幾乎可以肯定至少：在CenterPoint設計的效果，如果它不是控制的實際中心，以抵消控制邊界的交叉之外。如果這是您的意圖，請不要閱讀本段的其餘部分。如果這不是你的意圖，你可以重寫UpdateXYProperties()如下而失去CenterPoint屬性：

protected void UpdateXYProperties() 
{ 
    X1 = 0; 
    X2 = (float)ActualWidth; 
    Y1 = 0; 
    Y2 = (float)ActualHeight; 
} 

但是，這是給你和聖安德魯斯。

Answer 2

如果你希望綁定到X1，X2，Y1和Y2只讀屬性得到刷新時中心點依賴屬性被設置爲一個新的值UserControl應該實現INotifyPropertyChanged接口。然後，您可以註冊的依賴屬性PropertyChangedCallback，提高爲只讀屬性PropertyChanged事件：

public partial class Cross : UserControl, INotifyPropertyChanged 
{ 
    public Cross() 
    { 
     InitializeComponent(); 
    } 

    public readonly static DependencyProperty CenterPointProperty = DependencyProperty.Register("CenterPoint", 
     typeof(PointF), typeof(Cross), 
     new PropertyMetadata(default(PointF), new PropertyChangedCallback(OnCenterPointUpdated)))); 

    private static void OnCenterPointUpdated(DependencyObject d, DependencyPropertyChangedEventArgs e) 
    { 
     Cross cross = d as Cross; 
     cross.NotifyPropertyChanged("X1"); 
     cross.NotifyPropertyChanged("X2"); 
     cross.NotifyPropertyChanged("Y1"); 
     cross.NotifyPropertyChanged("Y2"); 
    } 

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

    ... 
}