WPF无法从代码访问DependencyProperty
我使用的是WPF4.5.2、.NET4.7.2、C#7 这是我的附加属性基类的代码WPF无法从代码访问DependencyProperty,wpf,attached-properties,Wpf,Attached Properties,我使用的是WPF4.5.2、.NET4.7.2、C#7 这是我的附加属性基类的代码 public abstract class BaseAP<Parent, Property> where Parent : BaseAP<Parent , Property>, new() { #region Public Events /// <summary> /// Fire when the value
public abstract class BaseAP<Parent, Property> where Parent : BaseAP<Parent , Property>, new()
{
#region Public Events
/// <summary>
/// Fire when the value changes
/// </summary>
public event Action<DependencyObject , DependencyPropertyChangedEventArgs> ValueChanged = ( sender , e ) => { };
#endregion
#region Properties
/// <summary>
/// A singleton instance of the parent class
/// </summary>
public static Parent Instance { get; private set; } = new Parent();
#endregion
#region Attached Properties Definitions
/// <summary>
/// The Attached Property for this class
/// </summary>
public static readonly DependencyProperty ValueProperty = DependencyProperty.RegisterAttached( "Value" , typeof( Property ) , typeof( BaseAP<Parent , Property> ) , new PropertyMetadata( new PropertyChangedCallback( OnValuePropertyChanged ) ) );
/// <summary>
/// The callback event when the <see cref="ValueProperty"/> is changed
/// </summary>
/// <param name="d">The UI-Element that had it's property changed</param>
/// <param name="e">The arguments for the event</param>
private static void OnValuePropertyChanged( DependencyObject d , DependencyPropertyChangedEventArgs e )
{
// --- Call the parent function
Instance.OnValueChanged( d , e );
// --- Call the event listeners
Instance.ValueChanged( d , e );
}
/// <summary>
/// Gets the attached property
/// </summary>
/// <param name="d">The element to get the property from</param>
/// <returns></returns>
public static Property GetValue( DependencyObject d )
{
return ( (Property) d.GetValue( ValueProperty ) );
}
/// <summary>
/// Sets the attached property
/// </summary>
/// <param name="d">The element to set the property to</param>
/// <param name="value">The value to set to the element</param>
public static void SetValue( DependencyObject d , Property value )
{
d.SetValue( ValueProperty , value );
}
#endregion
#region Event Methods
/// <summary>
/// The method is called when any attached property of this type is changed
/// </summary>
/// <param name="d">The ui element that this property was changed for</param>
/// <param name="e">The arguments for this event</param>
public virtual void OnValueChanged( DependencyObject d , DependencyPropertyChangedEventArgs e )
{
SetValue( d , (Property) e.NewValue );
}
#endregion
}
不幸的是,targetType总是空的
我做错了什么
感谢使用avance设置
值
附加属性后,您应该在用户控件
上调用获取值
:
Type type = uc.GetValue(APType.ValueProperty) as Type;
XAML:
<UserControl x:Name="uc" local:APType.Value="{x:Type local:SomeType}">
在创建
UserControl
之前,无法设置属性。在哪里调用GetValue
?在UserControl的代码隐藏中,可以将泛型参数属性设置为任何类型。我正在使用它,例如用于布尔、int甚至自定义类。在这个特殊的例子中,我指的是Type,因为我需要访问local:sometype的一些元数据。在构建UserControl
之前,无法设置该属性。正如我在回答中所说的,如果你在物业被损坏后再打电话给它,它会正常工作。不要再破坏这个问题。
Type targetType = GetValue( APType.ValueProperty ) as Type;
Type type = uc.GetValue(APType.ValueProperty) as Type;
<UserControl x:Name="uc" local:APType.Value="{x:Type local:SomeType}">