COMP 9TH MONTHLY

• Event


  • Typically used to signal user actions such as button clicks or menu selections in graphical user interfaces
  • When an event has multiple subscribers, the event handlers are invoked synchronously when an event is raised
  • For example, when a user clicks a control on a form, the form can raise a Click event and call a procedure that handles the event
• Event Handler


  Is a function or method containing a program statement that is executed in response to the event
• Event


  Is the action done using an input device
• Event Handler


  Is the interpretation of the event, the response, the reaction and the action triggered due to the event
• Some events


  • Change
  • Click
  • DblClick
  • DragDrop
  • DragOver
  • GotFocus
  • KeyDown
  • KeyPress
  • KeyUp
  • LostFocus
  • MouseDown
  • MouseMove
  • MouseUp
• Click Event


  Gets activated when a button is clicked on
• Object keyword


  The object that activates the event, placed in variable named sender
• ToString method


  Used on the sender variable
• EventArgs e


  The other argument in between the round brackets, considered as short for event arguments
• MouseDown Event


  • Recognizes which button of the mouse is pressed
  • Events or Bolt icon is the properties window
• Code Stub


  Automatically generated framework of a code procedure to be developed based on the event
• Event Handler


  This is the function or method containing a program statement that is executed in response to the event. It is usually a software routine that will process actions such as a keystroke and mouse movement.
• GotFocus


  This event when an element has the focus either by stop or the mouse pointer is hovering about the element.
• Click


   This event when the user selects an element using the primary mouse button
• Change


  This event occurs when the user edits the text displayed in the text box and combo box.
• MouseDown

  This event occurs when the user clicks a mouse button while the mouse pointer is over an object.
• Events


  These are built-in codes that get activated when a user performs an action on an object using any input device.
• KeyDown


   This event occurs when a key is pressed while the element has the focus.
• KeyPress


  This event occurs when key is pressed and released while the lament has the focus
• Double-Click


  This event occurs when you point at an element then clicking in quick succession the primary mouse button.
• Code Stub


  This is an automatically generated framework of a code procedure to be developed based on the event.
• Change


   occurs when the user edits the text displayed in the text box and combo box.
• Click 


  occurs when the user clicks/selects an element using the primary mouse button.
• DblClick


  occurs when the user double-clicks an element using the primary mouse button (pointing at an element then clicking the primary mouse button in quick succession)
• DragDrop


  occurs when the user drags (click, hold, and move to the desired location then release) an element to another location.
• DragOver


  occurs when the drags (click, hold and move over) an element over another control.
• GotFocus


  occurs when an element has the focus either by tab stop or the mouse pointer is hovering above the element.
• KeyDown 


  occurs when the key is pressed while the element has the focus.
• KeyPress


   occurs when a key is pressed and released while the element has the focus.
• KeyUp


  occurs when a key is released while the element has the focus.
• LostFocus


  occurs when an element loses the focus.
• MouseDown 


  occurs when the user clicks a mouse button while the mouse pointer is over an object.
• MouseMove


  occurs when the user moves the mouse over an element.
• MouseUp


  occurs when the user releases a mouse button while the pointer is over an object.
• ToString example?

  MessageBox.Show(sender.ToString());
• Message displays which object was the sender of the event and displays the text property of the sender.
• EventArgs e


  The other argument in between the round brackets
• MOUSEDOWN EVENT


  Recognizes which button of the mouse is pressed.
• Events or Bolt icon


   is the properties window
• EventsArgs


  is a class