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.
Not
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. |
Not
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