DependencyObject Class

Reference

Definition

Namespace:: System.Windows

Assembly:: WindowsBase.dll

Important

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Represents an object that participates in the dependency property system.

public ref class DependencyObject : System::Windows::Threading::DispatcherObject

public class DependencyObject : System.Windows.Threading.DispatcherObject

[System.Windows.Markup.NameScopeProperty("NameScope", typeof(System.Windows.NameScope))]
public class DependencyObject : System.Windows.Threading.DispatcherObject

type DependencyObject = class
    inherit DispatcherObject

[<System.Windows.Markup.NameScopeProperty("NameScope", typeof(System.Windows.NameScope))>]
type DependencyObject = class
    inherit DispatcherObject

Public Class DependencyObject
Inherits DispatcherObject

Inheritance: Object

DispatcherObject
DependencyObject

Derived: System.Windows.ContentElement

System.Windows.Controls.DataGridColumn

System.Windows.Controls.GridViewColumn

System.Windows.Controls.Ribbon.Primitives.StarLayoutInfo

System.Windows.Controls.TextSearch

More…

Attributes: NameScopePropertyAttribute

Examples

The following example derives from DependencyObject to create a new abstract class. The class then registers an attached property and includes support members for that attached property.

public abstract class AquariumObject3 : DependencyObject
{
    public enum Bouyancy
    {
        Floats,
        Sinks,
        Drifts
    }
    public static readonly DependencyProperty BouyancyProperty = DependencyProperty.RegisterAttached(
      "Bouyancy",
      typeof(Bouyancy),
      typeof(AquariumObject3),
      new FrameworkPropertyMetadata(Bouyancy.Floats, FrameworkPropertyMetadataOptions.AffectsArrange),
      new ValidateValueCallback(ValidateBouyancy)
    );
    public static void SetBouyancy(UIElement element, Bouyancy value)
    {
        element.SetValue(BouyancyProperty, value);
    }
    public static Bouyancy GetBouyancy(UIElement element)
    {
        return (Bouyancy)element.GetValue(BouyancyProperty);
    }
    private static bool ValidateBouyancy(object value)
    {
        Bouyancy bTest = (Bouyancy) value;
        return (bTest == Bouyancy.Floats || bTest == Bouyancy.Drifts || bTest==Bouyancy.Sinks);
    }
    public static readonly DependencyProperty IsDirtyProperty = DependencyProperty.Register(
      "IsDirty",
      typeof(Boolean),
      typeof(AquariumObject3)
    );
}

Public MustInherit Class AquariumObject3
    Inherits DependencyObject
    Public Enum Bouyancy
        Floats
        Sinks
        Drifts
    End Enum
    Public Shared ReadOnly BouyancyProperty As DependencyProperty = DependencyProperty.RegisterAttached("Bouyancy", GetType(Bouyancy), GetType(AquariumObject3), New FrameworkPropertyMetadata(Bouyancy.Floats, FrameworkPropertyMetadataOptions.AffectsArrange), New ValidateValueCallback(AddressOf ValidateBouyancy))
    Public Shared Sub SetBouyancy(ByVal element As UIElement, ByVal value As Bouyancy)
        element.SetValue(BouyancyProperty, value)
    End Sub
    Public Shared Function GetBouyancy(ByVal element As UIElement) As Bouyancy
        Return CType(element.GetValue(BouyancyProperty), Bouyancy)
    End Function
    Private Shared Function ValidateBouyancy(ByVal value As Object) As Boolean
        Dim bTest As Bouyancy = CType(value, Bouyancy)
        Return (bTest = Bouyancy.Floats OrElse bTest = Bouyancy.Drifts OrElse bTest = Bouyancy.Sinks)
    End Function
    Public Shared ReadOnly IsDirtyProperty As DependencyProperty = DependencyProperty.Register("IsDirty", GetType(Boolean), GetType(AquariumObject3))
End Class

Remarks

The DependencyObject class enables Windows Presentation Foundation (WPF) property system services on its many derived classes.

The property system's primary function is to compute the values of properties, and to provide system notification about values that have changed. Another key class that participates in the property system is DependencyProperty. DependencyProperty enables the registration of dependency properties into the property system, and provides identification and information about each dependency property, whereas DependencyObject as a base class enables objects to use the dependency properties.

DependencyObject services and characteristics include the following:

Dependency property hosting support. You register a dependency property by calling the Register method, and storing the method's return value as a public static field in your class.
Attached property hosting support. You register an attached property by calling the RegisterAttached method, and storing the method's return value as a public static read-only field in your class. (There are also additional member requirements; note that this represents a WPF specific implementation for attached properties. For details, see Attached Properties Overview.) Your attached property can then be set on any class that derives from DependencyObject.
Get, set, and clear utility methods for values of any dependency properties that exist on the DependencyObject.
Metadata, coerce value support, property changed notification, and override callbacks for dependency properties or attached properties. Also, the DependencyObject class facilitates the per-owner property metadata for a dependency property.
A common base class for classes derived from ContentElement, Freezable, or Visual. (UIElement, another base element class, has a class hierarchy that includes Visual.)

Constructors

DependencyObject()

Initializes a new instance of the DependencyObject class.

Properties

DependencyObjectType	Gets the DependencyObjectType that wraps the CLR type of this instance.
Dispatcher	Gets the Dispatcher this DispatcherObject is associated with. (Inherited from DispatcherObject)
IsSealed	Gets a value that indicates whether this instance is currently sealed (read-only).

Methods

CheckAccess()	Determines whether the calling thread has access to this DispatcherObject. (Inherited from DispatcherObject)
ClearValue(DependencyProperty)	Clears the local value of a property. The property to be cleared is specified by a DependencyProperty identifier.
ClearValue(DependencyPropertyKey)	Clears the local value of a read-only property. The property to be cleared is specified by a DependencyPropertyKey.
CoerceValue(DependencyProperty)	Coerces the value of the specified dependency property. This is accomplished by invoking any CoerceValueCallback function specified in property metadata for the dependency property as it exists on the calling DependencyObject.
Equals(Object)	Determines whether a provided DependencyObject is equivalent to the current DependencyObject.
GetHashCode()	Gets a hash code for this DependencyObject.
GetLocalValueEnumerator()	Creates a specialized enumerator for determining which dependency properties have locally set values on this DependencyObject.
GetType()	Gets the Type of the current instance. (Inherited from Object)
GetValue(DependencyProperty)	Returns the current effective value of a dependency property on this instance of a DependencyObject.
InvalidateProperty(DependencyProperty)	Re-evaluates the effective value for the specified dependency property.
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
OnPropertyChanged(DependencyPropertyChangedEventArgs)	Invoked whenever the effective value of any dependency property on this DependencyObject has been updated. The specific dependency property that changed is reported in the event data.
ReadLocalValue(DependencyProperty)	Returns the local value of a dependency property, if it exists.
SetCurrentValue(DependencyProperty, Object)	Sets the value of a dependency property without changing its value source.
SetValue(DependencyProperty, Object)	Sets the local value of a dependency property, specified by its dependency property identifier.
SetValue(DependencyPropertyKey, Object)	Sets the local value of a read-only dependency property, specified by the DependencyPropertyKey identifier of the dependency property.
ShouldSerializeProperty(DependencyProperty)	Returns a value that indicates whether serialization processes should serialize the value for the provided dependency property.
ToString()	Returns a string that represents the current object. (Inherited from Object)
VerifyAccess()	Enforces that the calling thread has access to this DispatcherObject. (Inherited from DispatcherObject)

Applies to

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