Create a Visual Basic. NET Control from scratch (vii)

visual| Create | Control step 6th: Clean up
For the control to work smoothly, we also need to do some other things. For example, the control needs to be redrawn when the size changes. And, in order not to change the proportions of the controls, we need to detect when the properties that affect the size change, and then force the width equal to One-third of the height. The following is an event handler that completes both tasks:

Private Sub trafficlight_resize (ByVal sender as Object, _
ByVal e as System.EventArgs) Handles mybase.resize
Me.invalidate ()
End Sub

Private Sub trafficlight_layout (ByVal sender as Object, _
ByVal e as System.Windows.Forms.LayoutEventArgs) _
Handles Mybase.layout
Select Case E.affectedproperty
Case "Bounds"
Me.Width = CInt (Me.height * 0.3333)
Case Else
' Do not perform any action
End Select
End Sub

Finally, set the icon that the control uses in the Toolbox. The control already has a default icon that looks like a gear, but we want to use the traffic light icon that is included with Visual Studio. NET.

The Toolbox icon for a control is set by an attribute in the class named ToolboxBitmap. Insert the following line above the line starting with public Class:

<toolboxbitmap ("C:\Program Files\Microsoft Visual Studio
. net\common7\graphics\icons\traffic\trffc09. ICO ") > _

Note: All content should be on one line. To facilitate reading, we placed a carriage return after Studio. When you paste the code, make sure that they are on a single line, just a space between Studio and. NET, and delete the carriage return. If you have installed Visual Studio. NET to its default location, the code above will set the attribute with an icon in the Visual Studio directory. If you do not install Visual Studio. NET to its default location, you will need to change the path name of the icon accordingly.