Shape.OnKeyDown Method (KeyEventArgs)

Article
09/30/2015

Raises the KeyDown event.

Namespace: Microsoft.VisualBasic.PowerPacks
Assembly: Microsoft.VisualBasic.PowerPacks.Vs (in Microsoft.VisualBasic.PowerPacks.Vs.dll)

Syntax

protected internal virtual void OnKeyDown(
    KeyEventArgs e
)

public protected:
virtual void OnKeyDown(
    KeyEventArgs^ e
)

abstract OnKeyDown : 
        e:KeyEventArgs -> unit
override OnKeyDown : 
        e:KeyEventArgs -> unit

Protected Friend Overridable Sub OnKeyDown (
    e As KeyEventArgs
)

Parameters

e
Type: System.Windows.Forms.KeyEventArgs

A KeyEventArgs that contains the event data.

Remarks

Raising an event invokes the event handler through a delegate. For more information, see Handling and Raising Events.

The OnKeyDown method also enables derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.

Notes to Inheritors:

When you override OnKeyDown in a derived class, be sure to call the OnKeyDown method of the base class so that registered delegates receive the event.

Examples

The following example is a method that is executed when the Click event occurs. The Shape class has several methods with the name pattern OnEventName that execute methods when the EventName event occurs. (EventName represents the name of the corresponding event.)

The following example demonstrates how to override the OnClick and OnLostFocus methods in a class that derives from LineShape.

public class HighlightLine :
    LineShape
{
    protected override void OnClick(EventArgs e)
    {
        // Change the color of the line when clicked.
        this.BorderColor = Color.Red;
        base.OnClick(e);
    }
    protected override void OnLostFocus(System.EventArgs e)
    {
        // Change the color of the line when focus is changed.
        this.BorderColor = Color.Black;
        base.OnLostFocus(e);
    }
}

Public Class HighlightLine
    Inherits LineShape
    Protected Overrides Sub OnClick(ByVal e As EventArgs)
        ' Change the color of the line when clicked.
        Me.BorderColor = Color.Red
        MyBase.OnClick(e)
    End Sub
    Protected Overrides Sub OnLostFocus(ByVal e As System.EventArgs)
        ' Change the color of the line when focus is changed.
        Me.BorderColor = Color.Black
        MyBase.OnLostFocus(e)
    End Sub
End Class