觸發器中的只讀附屬屬性（WPF）

Question

我遇到只讀附加屬性的問題。 我這樣定義它：

public class AttachedPropertyHelper : DependencyObject 
{ 

    public static readonly DependencyPropertyKey SomethingPropertyKey = DependencyProperty.RegisterAttachedReadOnly("Something", typeof(int), typeof(AttachedPropertyHelper), new PropertyMetadata(0)); 

    public static readonly DependencyProperty SomethingProperty = SomethingPropertyKey.DependencyProperty; 

} 

而且我想在XAML中使用它：

<Trigger Property="m:AttachedPropertyHelper.Something" Value="0"> 
         <Setter Property="FontSize" Value="20"/> 
        </Trigger> 

但是編譯器不想要與它合作。 在結果，我有2個錯誤：

無法找到樣式屬性的類型「東西」「ReadonlyAttachedProperty.AttachedPropertyHelper」。 Line 11 Position 16.

Property'Something'在'TextBlock'類型中找不到。

Answer 1

我不知道是否有一些特別的東西與你的只讀附加屬性，但如果你在默認的方式宣告其工作原理：

public class AttachedPropertyHelper : DependencyObject 
{ 
    public static int GetSomething(DependencyObject obj) 
    { 
     return (int)obj.GetValue(SomethingProperty); 
    } 

    public static void SetSomething(DependencyObject obj, int value) 
    { 
     obj.SetValue(SomethingProperty, value); 
    } 

    // Using a DependencyProperty as the backing store for Something. This enables animation, styling, binding, etc... 
    public static readonly DependencyProperty SomethingProperty = 
     DependencyProperty.RegisterAttached("Something", typeof(int), typeof(AttachedPropertyHelper), new UIPropertyMetadata(0)); 
} 

編輯

如果您想將其更改爲只讀屬性，請將其更改爲：

public class AttachedPropertyHelper : DependencyObject 
{ 
    public static int GetSomething(DependencyObject obj) 
    { 
     return (int)obj.GetValue(SomethingProperty); 
    } 

    internal static void SetSomething(DependencyObject obj, int value) 
    { 
     obj.SetValue(SomethingPropertyKey, value); 
    } 

    private static readonly DependencyPropertyKey SomethingPropertyKey = 
     DependencyProperty.RegisterAttachedReadOnly("Something", typeof(int), typeof(AttachedPropertyHelper), new UIPropertyMetadata(0)); 

    public static readonly DependencyProperty SomethingProperty = SomethingPropertyKey.DependencyProperty; 
}