Working with Events - Beginning C# 2008 Databases: From Novice to Professional - page 392

is raised. Events can have event-specific data (for example, a mouse-down event can
include data about the screen cursor's location).
The event handler signature observes the following conventions:

• The return type is Void .

• The first parameter is named sender and is of type Object . This represents the
object that raised the event.

• The second parameter is named e and is of type EventArgs or a derived class of
EventArgs . This represents the event-specific data.

• The event takes only these two parameters.

Common Events Raised by Controls

Various controls come with Visual Studio 2008, and they are built to achieve different
functionality from one another. However, the industry has identified a few events that are
common among many controls, and most applications use only these types of controls.
Table 17-1 describes the common events among various controls.

Table 17-1. Common Events

Event Name Description

Click

Usually occurs on left mouse click. This event can also occur with keyboard
input in the situation when the control is selected and the Enter key is pressed.

DoubleClick

Occurs when left mouse button is clicked twice rapidly.

KeyDown

Occurs when a key is pressed and a control has the focus.

KeyPress

Occurs when a key is pressed and a control has the focus.

KeyUp

Occurs when a key is released and a control has the focus.

MouseClick

Occurs only when a control is being clicked by the mouse.

MouseDoubleClick

Occurs when a control gets double-clicked by the mouse.

MouseDown

Occurs when the mouse pointer is located over a control and the mouse
button is being clicked.

MouseUp

Occurs when a mouse button is released over a control.

MouseEnter

Occurs when the mouse pointer enters a control.

MouseHover

Occurs when the mouse pointer is positioned over a control.

MouseLeave

Occurs when the mouse pointer rests on a control.

MouseMove

Occurs when the mouse rotates or moves over a control.

MouseWheel

Occurs when the user revolves the mouse wheel and a control has the focus.