Handling User Input

This topic describes the main keyboard and mouse events provided by System.Windows.Forms.Control. 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, see Raising Events from a Component.

Note
If there is no data associated with an event, an instance of the base class EventArgs is passed as an argument to the OnEventName method.

Keyboard 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
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.

Mouse Events

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 Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
    MyBase.OnMouseDown(e)
    If Not (myAllowUserEdit) Then
        Return
    End If
    Capture = True
    dragging = True
    SetDragValue(New Point(e.X, e.Y))
End Sub

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.

Protected Overrides Sub OnMouseMove(ByVal e As MouseEventArgs)
    MyBase.OnMouseMove(e)
    If (Not myAllowUserEdit Or Not dragging) Then
        Return
    End If
    SetDragValue(New Point(e.X, e.Y))
End Sub

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.

Protected Overrides Sub OnMouseUp(ByVal e As MouseEventArgs)
    MyBase.OnMouseUp(e)
    If (Not myAllowUserEdit Or Not dragging) Then
        Return
    End If
    Capture = False
    dragging = False
    Value = dragValue
    OnValueChanged(EventArgs.Empty)
End Sub

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 sample, see How to: Create a Windows Forms Control That Shows Progress.

See Also

Concepts

Events in Windows Forms Controls
Defining an Event in Windows Forms Controls

Other Resources

Handling and Raising Events
User Input in Windows Forms