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Handling User Input

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

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

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

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

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

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

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

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

For the complete source code for the FlashTrackBar sample, see How to: Create a Windows Forms Control That Shows Progress.

See also