12.2. Event Argument Reference The signature for event handlers is primarily the same for all events; only the event argument changes for different types of events. The syntax for all event handlers is: C#: public void HandlerName(Object sender, EventArgs e) Visual Basic: Sub HandlerName(ByVal sender As Object, ByVal e As EventArgs)
Each event argument type holds values specific to the event as well as general data such as the source element and the original source element. This section details the event argument types.
RoutedEventArgs is the base class for many other routed event argument types and is also the argument type passed to the event handler for events such as Click and Closed. Properties
Handled This Boolean designates whether the event has been handled. If it is set to true, then no other event handlers will be invoked.
OriginalSource OriginalSource is stored as an Object and is generally cast to FrameworkElement in order to determine its true type. OriginalSource is the original element that raised the event.
RoutedEvent This RoutedEvent type indicates the associated routed event. This value can never be null.
Source Source is stored as an Object, and is generally cast to FrameworkElement in order to determine its true type. Because of routing strategies, Source may not be the original source of the event. | DependencyPropertyChangedEventArgs | |
DependencyPropertyChangedEventArgs is passed to handlers that are raised when a dependency property changes. It is not associated with routed events. DependencyProp-ertyChangedEventArgs has properties that help to determine both the old value and new attribute values. This class also allows you to programmatically determine the state of a selector, such as CheckBox or RadioButton, as well as handle changes in other properties. Properties
NewValue NewValue is an Object that can be cast to the appropriate type. NewValue holds the new value of the property.
OldValue OldValue is an Object that can be cast to the appropriate type. OldValue holds the previous value of the property.
Property This field returns the actual property that has been changed, allowing you to programmatically manipulate it.
PropertyName This String represents the name of the property that has been changed.
KeyEventArgs describes the arguments passed to a handler for a key-based event, such as KeyUp or KeyDown. Properties
Device This property gets or sets the InputDevice that raised the event.
Handled This Boolean designates whether the event has been handled. If it is set to true, then no other event handlers will be invoked.
InputSource This property is the PresentationSource that raised the event. At this time, there is only one implementation of a presentation source: the Windows standard HwndSource.
IsDown This Boolean indicates whether the key referenced by the event is down.
IsRepeat This Boolean indicates whether the key referenced by the event is a repeated key.
IsToggled This Boolean indicates whether the key referenced by the event is toggled.
IsUp This Boolean indicates whether the key referenced by the event is up.
Key This Key (enumeration) indicates the key referenced by the event. See Microsoft's documentation for Key enumeration values.
KeyboardDevice KeyboardDevice contains the logical KeyboardDevice.
KeyState This KeyState (enumeration containing Down, None, Toggled) indicates the state of the key associated with the event.
OriginalSource OriginalSource is stored as an Object and is generally cast to FrameworkElement in order to determine its true type. OriginalSource is the original element that raised the event.
RoutedEvent This property indicates the associated routed event. This value can never be null.
Source Source is stored as an Object and is generally cast to FrameworkElement in order to determine its true type. Because of routing strategies, Source may not be the original source of the event.
SystemKey This property indicates the Key associated with this event if the event is going to be processed by the system.
TimeStamp This property is an Integer representing the time the event occurred.
ScrollChangedEventArgs is derived from RoutedEventArgs and extends the class with properties specific to scrollbars. Properties
HorizontalChange A Double value indicating the amount of horizontal change in the scrolled content
HorizontalOffset A Double value indicating the updated horizontal position of the content
VerticalChange A Double value indicating the amount of vertical change in the scrolled content
VerticalOffset A Double value indicating the updated vertical position of the content
TextChangedEventArgs is derived from RoutedEventArgs and adds properties specific to the TextChanged event Properties
UndoAction UndoAction is an enumeration indicating how the change in text will affect the undo stack.
Clear The action will clear the undo stack.
Create The action will create a new undo stack.
Merge This change will merge into the previous undo stack.
None This change will not affect the undo stack.
Redo This change is the result of a call to Redo( ).
Undo This change is the result of a call to Undo( ).
MouseEventArgs provide access to the mouse and its various states. Properties
Device This property gets or sets the InputDevice that raised the event.
Handled This Boolean designates whether the event has been handled. If it is set to true, then no other event handlers will be invoked.
LeftButton This MouseButtonState (an enumeration containing Pressed and Released) indicates the state of the left button of the mouse.
MiddleButton This MouseButtonState (an enumeration containing Pressed and Released) indicates the state of the middle button of the mouse.
MouseDevice This property gets the MouseDevice associated with the event.
OriginalSource OriginalSource is stored as an Object and is generally cast to FrameworkElement in order to determine its true type. OriginalSource is the original element that raised the event.
RightButton This MouseButtonState (an enumeration containing Pressed and Released) indicates the state of the right button of the mouse.
RoutedEvent This property indicates the associated routed event. This value can never be null.
Source Source is stored as an Object and is generally cast to type FrameworkElement in order to determine its true type. Because of routing strategies, Source may not be the original source of the event.
StylusPointer This Object represents the stylus mouse associated with the event.
TimeStamp This Integer represents the time the event occurred.
XButton1 This MouseButtonState (an enumeration containing Pressed and Released) indicates the state of the first extended button of the mouse.
XButton2 This MouseButtonState (an enumeration containing Pressed and Released) indicates the state of the second extended button of the mouse.
MouseButtonEventArgs extends MouseEventArgs and adds several properties dealing specifically with the mouse buttons. It is generally used by non-routed mouse button events such as MouseLeftButtonDown and MouseLeftButtonUp. Properties
ButtonState This property is read-only and indicates the MouseButtonState (Pressed or Released) of the mouse button associated with the event.
ChangedButton This property is read-only and indicates which MouseButton (an enumeration containing Left, Middle, Right, XButton1, or XButton2) has changed.
ClickCount This Integer indicates the click count of the button associated with the event. | SelectionChangedEventArgs | |
SelectionChangedEventArgs is derived from RoutedEventArgs and adds properties specific to the SelectionChanged event. Properties
SelectedItems SelectedItems is an IList (a non-generic collection of objects that can be accessed by index) of all items selected as a result of this event.
UnselectedItems UnselectedItems is an IList (a non-generic collection of objects that can be accessed by index) of all items unselected as a result of this event. |
