DependencyPropertyChangedEventArgs Struct

Definizione

Fornisce i dati per diversi eventi di modifica delle proprietà.Provides data for various property changed events. Questi eventi segnalano in genere effettive modifiche del valore di una proprietà di dipendenza di sola lettura.Typically these events report effective value changes in the value of a read-only dependency property. Un altro utilizzo è come parte di un'implementazione PropertyChangedCallback.Another usage is as part of a PropertyChangedCallback implementation.

public value class DependencyPropertyChangedEventArgs
public struct DependencyPropertyChangedEventArgs
type DependencyPropertyChangedEventArgs = struct
Public Structure DependencyPropertyChangedEventArgs
Ereditarietà
DependencyPropertyChangedEventArgs

Esempi

Nell'esempio seguente viene usata DependencyPropertyChangedEventArgs la classe nel contesto di un PropertyChangedCallback oggetto per una particolare proprietà di una classe personalizzata che definisce anche gli eventi.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. Il callback accetta i risultati dei valori vecchi e nuovi dal sistema di proprietà come comunicati da DependencyPropertyChangedEventArgse li riassembla in una classe RoutedPropertyChangedEventArgs<T>di argomenti di eventi diversi.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>. I nuovi argomenti vengono quindi usati come dati per un evento "ValueChanged" definito da e generati dalla classe personalizzata.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

Commenti

Gli eventi che usano la DependencyPropertyChangedEventArgs classe per i dati dell'evento e DependencyPropertyChangedEventHandler le implementazioni del metodo per i gestori, in genere seguono Is*Changedil modello di denominazione e vengono Common Language Runtime (CLR)common language runtime (CLR) in genere RoutedEvent implementati come eventi senza backup (non si tratta di eventi indirizzati).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 Common Language Runtime (CLR)common language runtime (CLR) events without RoutedEvent backing (they are not routed events). Alcuni metodi di gestione delle classi che "gestiscono" eventi altrimenti non esposti che segnalano una modifica dello stato tramite una ButtonBase.OnIsPressedChangedmodifica di proprietà, DependencyPropertyChangedEventArgs ad esempio, usano anche la classe per i dati dell'evento.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.

Lo scenario per PropertyChangedCallback consiste nell'usare gli argomenti per segnalare i valori vecchi e nuovi che provengono dalla valutazione del sistema di proprietà della proprietà.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. Un callback che elabora i valori vecchi e nuovi può scegliere una gestione speciale a seconda di questi valori, ad esempio la scelta di non rispondere alle modifiche del valore ritenute non significative.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.

Costruttori

DependencyPropertyChangedEventArgs(DependencyProperty, Object, Object)

Inizializza una nuova istanza della classe DependencyPropertyChangedEventArgs.Initializes a new instance of the DependencyPropertyChangedEventArgs class.

Proprietà

NewValue

Ottiene il valore della proprietà dopo la modifica.Gets the value of the property after the change.

OldValue

Ottiene il valore della proprietà prima della modifica.Gets the value of the property before the change.

Property

Ottiene l'identificatore per la proprietà di dipendenza in cui si è verificata la modifica del valore.Gets the identifier for the dependency property where the value change occurred.

Metodi

Equals(DependencyPropertyChangedEventArgs)

Determina se l'oggetto DependencyPropertyChangedEventArgs specificato equivale all'oggetto DependencyPropertyChangedEventArgs corrente.Determines whether the provided DependencyPropertyChangedEventArgs is equivalent to the current DependencyPropertyChangedEventArgs.

Equals(Object)

Determina se l'oggetto specificato equivale all'oggetto DependencyPropertyChangedEventArgs corrente.Determines whether the provided object is equivalent to the current DependencyPropertyChangedEventArgs.

GetHashCode()

Ottiene un codice hash per l'oggetto DependencyPropertyChangedEventArgs.Gets a hash code for this DependencyPropertyChangedEventArgs.

Operatori

Equality(DependencyPropertyChangedEventArgs, DependencyPropertyChangedEventArgs)

Determina se due oggetti DependencyPropertyChangedEventArgs specificati hanno lo stesso valore.Determines whether two specified DependencyPropertyChangedEventArgs objects have the same value.

Inequality(DependencyPropertyChangedEventArgs, DependencyPropertyChangedEventArgs)

Determina se due oggetti DependencyPropertyChangedEventArgs specificati sono diversi.Determines whether two specified DependencyPropertyChangedEventArgs objects are different.

Si applica a

Vedi anche