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UIElement Class

UIElement is a base class for most of the objects that have visual appearance and can process basic input in Silverlight.

Inheritance Hierarchy

System.Object
  System.Windows.DependencyObject
    System.Windows.UIElement
      System.Windows.FrameworkElement

Namespace: System.Windows
Assembly: System.Windows (in System.Windows.dll)

Syntax

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public abstract class UIElement : DependencyObject

The UIElement type exposes the following members.

Properties

	Name	Description
	AllowDrop	Gets or sets a value that determines whether this UIElement can be a drop target for purposes of Silverlight drag-and-drop operations.
	CacheMode	Gets or sets a value that indicates that rendered content should be cached when possible.
	Clip	Gets or sets the Geometry used to define the outline of the contents of a UIElement.
	DesiredSize	Gets the size that this UIElement computed during the measure pass of the layout process.
	Dispatcher	Gets the Dispatcher this object is associated with. (Inherited from DependencyObject.)
	Effect	Gets or sets the pixel shader effect to use for rendering this UIElement.
	IsHitTestVisible	Gets or sets whether the contained area of this UIElement can return true values for hit testing.
	Opacity	Gets or sets the degree of the object's opacity.
	OpacityMask	Gets or sets the brush used to alter the opacity of regions of this object.
	Projection	Gets or sets the perspective projection (3-D effect) to apply when rendering this UIElement.
	RenderSize	Gets the final render size of a UIElement.
	RenderTransform	Gets or sets transform information that affects the rendering position of a UIElement.
	RenderTransformOrigin	Gets or sets the origin point of any possible render transform declared by RenderTransform, relative to the bounds of the UIElement.
	UseLayoutRounding	Gets or sets a value that determines whether rendering for the object and its visual subtree should use rounding behavior that aligns rendering to whole pixels.
	Visibility	Gets or sets the visibility of a UIElement. A UIElement that is not visible does not render and does not communicate its desired size to layout.

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Methods

	Name	Description
	AddHandler	Adds a routed event handler for a specified routed event, adding the handler to the handler collection on the current element. Specify handledEventsToo as true to have the provided handler be invoked for routed event that had already been marked as handled by another element along the event route.
	Arrange	Positions child objects and determines a size for a UIElement. Parent objects that implement custom layout for their child elements should call this method from their layout override implementations to form a recursive layout update.
	CaptureMouse	Sets mouse capture to a UIElement.
	CheckAccess	Determines whether the calling thread has access to this object. (Inherited from DependencyObject.)
	ClearValue	Clears the local value of a dependency property. (Inherited from DependencyObject.)
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetAnimationBaseValue	Returns any base value established for a Silverlight dependency property, which would apply in cases where an animation is not active. (Inherited from DependencyObject.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	GetValue	Returns the current effective value of a dependency property from a DependencyObject. (Inherited from DependencyObject.)
	InvalidateArrange	Invalidates the arrange state (layout) for a UIElement. After the invalidation, the UIElement will have its layout updated, which will occur asynchronously.
	InvalidateMeasure	Invalidates the measurement state (layout) for a UIElement.
	Measure	Updates the DesiredSize of a UIElement. Typically, objects that implement custom layout for their layout children call this method from their own MeasureOverride implementations to form a recursive layout update.
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	OnCreateAutomationPeer	When implemented in a derived class, returns class-specific AutomationPeer implementations for the Silverlight automation infrastructure.
	ReadLocalValue	Returns the local value of a dependency property, if a local value is set. (Inherited from DependencyObject.)
	ReleaseMouseCapture	Removes mouse capture from a UIElement. After this call, typically no object holds mouse capture.
	RemoveHandler	Removes the specified routed event handler from this UIElement.
	SetValue	Sets the local value of a dependency property on a DependencyObject. (Inherited from DependencyObject.)
	ToString	Returns a string that represents the current object. (Inherited from Object.)
	TransformToVisual	Returns a transform object that can be used to transform coordinates from the UIElement to the specified object.
	UpdateLayout	Ensures that all positions of child objects of a UIElement are properly updated for layout.

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Events

	Name	Description
	DoubleTap	Occurs when a DoubleTap gesture is committed while over this UIElement.
	DragEnter	Occurs when the input system reports an underlying drag event with this element as the target.
	DragLeave	Occurs when the input system reports an underlying drag event with this element as the origin.
	DragOver	Occurs when the input system reports an underlying drag event with this element as the potential drop target.
	Drop	Occurs when the input system reports an underlying drop event with this element as the drop target.
	GotFocus	Occurs when a UIElement receives focus.
	Hold	Occurs when a Hold gesture is committed while over this UIElement.
	KeyDown	Occurs when a keyboard key is pressed while the UIElement has focus.
	KeyUp	Occurs when a keyboard key is released while the UIElement has focus.
	LostFocus	Occurs when a UIElement loses focus.
	LostMouseCapture	Occurs when the UIElement loses mouse capture.
	ManipulationCompleted	Occurs when a manipulation and inertia on the UIElement is complete.
	ManipulationDelta	Occurs when the input device changes position during a manipulation.
	ManipulationStarted	Occurs when an input device begins a manipulation on the UIElement.
	MediaCommand	Occurs when a button is pressed on a remote control.
	MouseEnter	Occurs when the mouse (or a stylus) enters the bounding area of a UIElement.
	MouseLeave	Occurs when the mouse (or the stylus) leaves the bounding area of a UIElement.
	MouseLeftButtonDown	Occurs when the left mouse button is pressed (or when the tip of the stylus touches the tablet) while the mouse pointer is over a UIElement.
	MouseLeftButtonUp	Occurs when the left mouse button is released (or the tip of the stylus is removed from the tablet) while the mouse (or the stylus) is over a UIElement (or while a UIElement holds mouse capture).
	MouseMove	Occurs when the coordinate position of the mouse (or stylus) changes while over a UIElement (or while a UIElement holds mouse capture).
	MouseRightButtonDown	Occurs when the right mouse button is pressed while the mouse pointer is over a UIElement.
	MouseRightButtonUp	Occurs when the right mouse button is released while the mouse pointer is over a UIElement. However, this event will only be raised if a caller marks the preceding MouseRightButtonDown event as handled; see Remarks.
	MouseWheel	Occurs when the user rotates the mouse wheel while the mouse pointer is over a UIElement, or the UIElement has focus.
	Tap	Occurs when a Tap gesture is committed while over this UIElement.
	TextInput	Occurs when a UI element gets text in a device-independent manner.
	TextInputStart	Occurs when a UI element initially gets text in a device-independent manner.
	TextInputUpdate	Occurs when text continues to be composed via an input method editor (IME).

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Fields

	Name	Description
	AllowDropProperty	Identifies the AllowDrop dependency property.
	CacheModeProperty	Identifies the CacheMode dependency property.
	ClipProperty	Identifies the Clip dependency property.
	DoubleTapEvent	Identifies the DoubleTap routed event.
	EffectProperty	Identifies the Effect dependency property.
	HoldEvent	Identifies the Hold routed event.
	IsHitTestVisibleProperty	Identifies the IsHitTestVisible dependency property.
	KeyDownEvent	Identifies the KeyDown routed event.
	KeyUpEvent	Identifies the KeyUp routed event.
	ManipulationCompletedEvent	Identifies the ManipulationCompleted routed event.
	ManipulationDeltaEvent	Identifies the ManipulationDelta routed event.
	ManipulationStartedEvent	Identifies the ManipulationStarted routed event.
	MouseLeftButtonDownEvent	Identifies the MouseLeftButtonDown routed event.
	MouseLeftButtonUpEvent	Identifies the MouseLeftButtonUp routed event.
	MouseRightButtonDownEvent	Identifies the MouseRightButtonDown routed event.
	MouseRightButtonUpEvent	Identifies the MouseRightButtonUp routed event.
	MouseWheelEvent	Identifies the MouseWheel routed event.
	OpacityMaskProperty	Identifies the IsHitTestVisible dependency property.
	OpacityProperty	Identifies the IsHitTestVisible dependency property.
	ProjectionProperty	Identifies the Projection dependency property.
	RenderTransformOriginProperty	Identifies the RenderTransformOrigin dependency property.
	RenderTransformProperty	Identifies the RenderTransform dependency property.
	TapEvent	Identifies the Tap routed event.
	TextInputEvent	Identifies the TextInput routed event.
	TextInputStartEvent	Identifies the TextInputStart routed event.
	TextInputUpdateEvent	Identifies the TextInputUpdate routed event.
	UseLayoutRoundingProperty	Identifies the UseLayoutRounding dependency property.
	VisibilityProperty	Identifies the Visibility dependency property.

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Remarks

UIElement provides a starting point for Silverlight layout characteristics; FrameworkElement adds more layout capabilities.

Much of the input behavior for visible elements in a Silverlight UI is defined in the UIElement class. This includes the events for keyboard, mouse and stylus input, and focus events. Some of these events are routed events. A routed event enables a built-in event handling notification system, so that a parent object can handle input events from child objects in the object tree if the event remains unhandled. This input event behavior is useful for input area grouping, and for control compositing.

Although UIElement defines the events for focus reporting (GotFocus, LostFocus), UIElement does not define an API for programmatically setting the focus. However, this capability is defined by the Control class and is thus present for many of the Silverlight elements in a UI.

UIElement does not expose a public constructor. It is not typical to derive from either UIElement or FrameworkElement directly. More typically used base classes for derived custom classes in Silverlight are these classes:

Specific controls that are not sealed (for example, TextBox)
Control base classes (Control, ContentControl, UserControl)
Panel classes (the base class Panel, or specific non-sealed panel implementations, for example Grid)