Shape.OnPreviewKeyDown Method

Raises the PreviewKeyDown event.

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

Syntax

'إقرار
Protected Friend Overridable Sub OnPreviewKeyDown ( _
    e As PreviewKeyDownEventArgs _
)
'الاستخدام
Dim e As PreviewKeyDownEventArgs

Me.OnPreviewKeyDown(e)

protected internal virtual void OnPreviewKeyDown(
    PreviewKeyDownEventArgs e
)

protected public:
virtual void OnPreviewKeyDown(
    PreviewKeyDownEventArgs^ e
)

abstract OnPreviewKeyDown : 
        e:PreviewKeyDownEventArgs -> unit 
override OnPreviewKeyDown : 
        e:PreviewKeyDownEventArgs -> unit 

 function OnPreviewKeyDown(
    e : PreviewKeyDownEventArgs
)

Parameters

• e
  Type: System.Windows.Forms.PreviewKeyDownEventArgs
  A PreviewKeyDownEventArgs that contains the event data.

Remarks

Raising an event invokes the event handler through a delegate. For more information, see Raising an Event.

The OnPreviewKeyDown 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 OnPreviewKeyDown in a derived class, be sure to call the OnPreviewKeyDown 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
    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

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);
    }
}

.NET Framework Security

• Full trust for the immediate caller. This member cannot be used by partially trusted code. For more information, see Using Libraries from Partially Trusted Code.

See Also

Reference

Shape Class

Shape Members

Microsoft.VisualBasic.PowerPacks Namespace

Other Resources

How to: Draw Lines with the LineShape Control (Visual Studio)

How to: Draw Shapes with the OvalShape and RectangleShape Controls (Visual Studio)

Introduction to the Line and Shape Controls (Visual Studio)