Handling User Input and Events

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Handling User Input and Events

When handling an event, control authors should override the protected OnEventName method rather than attaching a delegate to the event. For a review of events,


The common keyboard events that your control can handle are KeyDown, KeyPress, and KeyUp.

Event Name Method to Override Description of Event
KeyDown void OnKeyDown(KeyEventArgs) Raised only when a key is initially pressed.
KeyPress void OnKeyPress(KeyPressEventArgs) Raised every time a key is pressed. If a key is held down, a KeyPress event is raised at the repeat rate defined by the operating system.
KeyUp void OnKeyUp(KeyEventArgs) Raised when a key is released.
Note Note
Handling keyboard input is considerably more complex than overriding the events in the preceding table and is beyond the scope of this topic. For more information, see User Input in Windows Forms.

 

The mouse events that your control can handle are MouseDown, MouseEnter, MouseHover, MouseLeave, MouseMove, and MouseUp.

Event Name Method to Override Description of Event
MouseDown void OnMouseDown(MouseEventArgs) Raised when the mouse button is pressed while the pointer is over the control.
MouseEnter void OnMouseEnter(EventArgs) Raised when the pointer first enters the region of the control.
MouseHover void OnMouseHover(EventArgs) Raised when the pointer hovers over the control.
MouseLeave void OnMouseLeave(EventArgs) Raised when the pointer leaves the region of the control.
MouseMove void OnMouseMove(MouseEventArgs) Raised when the pointer moves in the region of the control.
MouseUp void OnMouseUp(MouseEventArgs) Raised when the mouse button is released while the pointer is over the control or the pointer leaves the region of the control.

The following code fragment shows an example of overriding the MouseDown event.

protected override void OnMouseDown(MouseEventArgs e) {
    base.OnMouseDown(e);
    if (!allowUserEdit) {
        return;
    }
    Capture = true;
    dragging = true;
    SetDragValue(new Point(e.X, e.Y));
}

The following code fragment shows an example of overriding the MouseMove event.

An C# example

protected override void OnMouseMove(MouseEventArgs e) {
    base.OnMouseMove(e);
    if (!allowUserEdit || !dragging) {
        return;
    }
    SetDragValue(new Point(e.X, e.Y));
}

The following code fragment shows an example of overriding the MouseUp event.

An C# example

protected override void OnMouseUp(MouseEventArgs e) {
    base.OnMouseUp(e);
    if (!allowUserEdit || !dragging) {
        return;
    }
    Capture = false;
    dragging = false;
    value = dragValue;
    OnValueChanged(EventArgs.Empty);
}

For the complete source code for the FlashTrackBar sampl

–MSDN

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