DependencyPropertyChangedEventArgs DependencyPropertyChangedEventArgs DependencyPropertyChangedEventArgs DependencyPropertyChangedEventArgs Struct

定义

提供各种属性更改事件的数据。Provides data for various property changed events. 通常这些事件对只读依赖属性的值中的有效值更改进行报告。Typically these events report effective value changes in the value of a read-only dependency property. 另一种用法是作为 PropertyChangedCallback 实现的一部分。Another usage is as part of a PropertyChangedCallback implementation.

public value class DependencyPropertyChangedEventArgs
public struct DependencyPropertyChangedEventArgs
type DependencyPropertyChangedEventArgs = struct
Public Structure DependencyPropertyChangedEventArgs
继承
DependencyPropertyChangedEventArgsDependencyPropertyChangedEventArgsDependencyPropertyChangedEventArgsDependencyPropertyChangedEventArgs

示例

下面的示例在的DependencyPropertyChangedEventArgs上下文PropertyChangedCallback中对也定义事件的自定义类的特定属性使用类。The following example uses the DependencyPropertyChangedEventArgs class in the context of a PropertyChangedCallback for a particular property of a custom class that also defines events. 回调从属性系统DependencyPropertyChangedEventArgs中获取旧值和新值的结果, 并将这些值重新打包到不同的事件参数类RoutedPropertyChangedEventArgs<T>中。The callback takes the results of old and new values from the property system as communicated by DependencyPropertyChangedEventArgs, and repackages these into a different events arguments class RoutedPropertyChangedEventArgs<T>. 然后, 新参数将用作定义的 "ValueChanged" 事件的数据, 并由自定义类引发。The new arguments are then used as the data for a "ValueChanged" event defined by and raised by the custom class.

public static readonly DependencyProperty ValueProperty =
    DependencyProperty.Register(
        "Value", typeof(decimal), typeof(NumericUpDown),
        new FrameworkPropertyMetadata(MinValue, new PropertyChangedCallback(OnValueChanged),
                                      new CoerceValueCallback(CoerceValue)));

private static object CoerceValue(DependencyObject element, object value)
{
    decimal newValue = (decimal)value;

    newValue = Math.Max(MinValue, Math.Min(MaxValue, newValue));

    return newValue;
}

private static void OnValueChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
{
    NumericUpDown control = (NumericUpDown)obj;

    RoutedPropertyChangedEventArgs<decimal> e = new RoutedPropertyChangedEventArgs<decimal>(
        (decimal)args.OldValue, (decimal)args.NewValue, ValueChangedEvent);
    control.OnValueChanged(e);
}
/// <summary>
/// Identifies the ValueChanged routed event.
/// </summary>
public static readonly RoutedEvent ValueChangedEvent = EventManager.RegisterRoutedEvent(
    "ValueChanged", RoutingStrategy.Bubble,
    typeof(RoutedPropertyChangedEventHandler<decimal>), typeof(NumericUpDown));

/// <summary>
/// Occurs when the Value property changes.
/// </summary>
public event RoutedPropertyChangedEventHandler<decimal> ValueChanged
{
    add { AddHandler(ValueChangedEvent, value); }
    remove { RemoveHandler(ValueChangedEvent, value); }
}
/// <summary>
/// Raises the ValueChanged event.
/// </summary>
/// <param name="args">Arguments associated with the ValueChanged event.</param>
protected virtual void OnValueChanged(RoutedPropertyChangedEventArgs<decimal> args)
{
    RaiseEvent(args);
}
Public Shared ReadOnly ValueProperty As DependencyProperty = DependencyProperty.Register("Value", GetType(Decimal), GetType(NumericUpDown), New FrameworkPropertyMetadata(MinValue, New PropertyChangedCallback(AddressOf OnValueChanged), New CoerceValueCallback(AddressOf CoerceValue)))

Private Shared Overloads Function CoerceValue(ByVal element As DependencyObject, ByVal value As Object) As Object
    Dim newValue As Decimal = CDec(value)

    newValue = Math.Max(MinValue, Math.Min(MaxValue, newValue))

    Return newValue
End Function

Private Shared Sub OnValueChanged(ByVal obj As DependencyObject, ByVal args As DependencyPropertyChangedEventArgs)
    Dim control As NumericUpDown = CType(obj, NumericUpDown)

    Dim e As New RoutedPropertyChangedEventArgs(Of Decimal)(CDec(args.OldValue), CDec(args.NewValue), ValueChangedEvent)
    control.OnValueChanged(e)
End Sub
''' <summary>
''' Identifies the ValueChanged routed event.
''' </summary>
Public Shared ReadOnly ValueChangedEvent As RoutedEvent = EventManager.RegisterRoutedEvent("ValueChanged", RoutingStrategy.Bubble, GetType(RoutedPropertyChangedEventHandler(Of Decimal)), GetType(NumericUpDown))

''' <summary>
''' Occurs when the Value property changes.
''' </summary>
Public Custom Event ValueChanged As RoutedPropertyChangedEventHandler(Of Decimal)
    AddHandler(ByVal value As RoutedPropertyChangedEventHandler(Of Decimal))
        MyBase.AddHandler(ValueChangedEvent, value)
    End AddHandler
    RemoveHandler(ByVal value As RoutedPropertyChangedEventHandler(Of Decimal))
        MyBase.RemoveHandler(ValueChangedEvent, value)
    End RemoveHandler
    RaiseEvent(ByVal sender As System.Object, ByVal e As RoutedPropertyChangedEventArgs(Of Decimal))
    End RaiseEvent
End Event
''' <summary>
''' Raises the ValueChanged event.
''' </summary>
''' <param name="args">Arguments associated with the ValueChanged event.</param>
Protected Overridable Sub OnValueChanged(ByVal args As RoutedPropertyChangedEventArgs(Of Decimal))
    MyBase.RaiseEvent(args)
End Sub

注解

使用事件数据的DependencyPropertyChangedEventArgs类的事件和处理程序的DependencyPropertyChangedEventHandler方法实现通常遵循命名模式Is*Changed, 并且通常作为公共语言运行时 (CLR)common language runtime (CLR)事件实现, 而不会RoutedEvent支持 (它们不是路由事件)。The events that use the DependencyPropertyChangedEventArgs class for event data, and the DependencyPropertyChangedEventHandler method implementations for handlers, generally follow the naming pattern Is*Changed, and are generally implemented as 公共语言运行时 (CLR)common language runtime (CLR) events without RoutedEvent backing (they are not routed events). 某些类处理方法, 这些方法 "处理" 其他不公开的事件 (这些事件通过属性更改报告状态ButtonBase.OnIsPressedChanged更改, 如) DependencyPropertyChangedEventArgs也将类用于事件数据。Some class handling methods that "handle" otherwise unexposed events that report a state change through a property change, such as ButtonBase.OnIsPressedChanged, also use the DependencyPropertyChangedEventArgs class for event data.

的方案PropertyChangedCallback是使用自变量报告属性系统计算属性中的旧值和新值。The scenario for PropertyChangedCallback is to use the arguments to report old and new values that come from the property system evaluation of the property. 处理旧值和新值的回调可能会根据这些值选择特殊处理, 例如选择不响应被视为不重要的值更改。A callback that processes old and new values might choose special handling depending on these values, such as choosing to not respond to value changes that are deemed insignificant.

构造函数

DependencyPropertyChangedEventArgs(DependencyProperty, Object, Object) DependencyPropertyChangedEventArgs(DependencyProperty, Object, Object) DependencyPropertyChangedEventArgs(DependencyProperty, Object, Object) DependencyPropertyChangedEventArgs(DependencyProperty, Object, Object)

初始化 DependencyPropertyChangedEventArgs 类的新实例。Initializes a new instance of the DependencyPropertyChangedEventArgs class.

属性

NewValue NewValue NewValue NewValue

获取发生更改之后的属性的值。Gets the value of the property after the change.

OldValue OldValue OldValue OldValue

获取发生更改之前的属性的值。Gets the value of the property before the change.

Property Property Property Property

获取发生值更改的依赖项属性的标识符。Gets the identifier for the dependency property where the value change occurred.

方法

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

确定提供的对象是否与当前 DependencyPropertyChangedEventArgs 相同。Determines whether the provided object is equivalent to the current DependencyPropertyChangedEventArgs.

Equals(DependencyPropertyChangedEventArgs) Equals(DependencyPropertyChangedEventArgs) Equals(DependencyPropertyChangedEventArgs) Equals(DependencyPropertyChangedEventArgs)

确定提供的 DependencyPropertyChangedEventArgs 是否与当前 DependencyPropertyChangedEventArgs 相同。Determines whether the provided DependencyPropertyChangedEventArgs is equivalent to the current DependencyPropertyChangedEventArgs.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

获取此 DependencyPropertyChangedEventArgs 的哈希代码。Gets a hash code for this DependencyPropertyChangedEventArgs.

操作员

Equality(DependencyPropertyChangedEventArgs, DependencyPropertyChangedEventArgs) Equality(DependencyPropertyChangedEventArgs, DependencyPropertyChangedEventArgs) Equality(DependencyPropertyChangedEventArgs, DependencyPropertyChangedEventArgs) Equality(DependencyPropertyChangedEventArgs, DependencyPropertyChangedEventArgs)

确定两个指定的 DependencyPropertyChangedEventArgs 对象是否具有相同的值。Determines whether two specified DependencyPropertyChangedEventArgs objects have the same value.

Inequality(DependencyPropertyChangedEventArgs, DependencyPropertyChangedEventArgs) Inequality(DependencyPropertyChangedEventArgs, DependencyPropertyChangedEventArgs) Inequality(DependencyPropertyChangedEventArgs, DependencyPropertyChangedEventArgs) Inequality(DependencyPropertyChangedEventArgs, DependencyPropertyChangedEventArgs)

确定两个指定的 DependencyPropertyChangedEventArgs 对象是否不同。Determines whether two specified DependencyPropertyChangedEventArgs objects are different.

适用于

另请参阅