Figures
© 2004 Microsoft Corporation. All rights reserved.
Figure 3 Custom Property in the Visual Basic Control
' Control properties. This is the interval at which the blinking label
' changes its color from on to off or back again, in seconds.

Private m_BlinkInterval As Integer = 1

Public Property BlinkInterval() As Integer
    Get
        Return m_BlinkInterval
    End Get

    ' Property has changed. Remember its new value, and set the 
    ' control's timer to use it. 

    Set(ByVal Value As Integer)
        m_BlinkInterval = Value
        myTimer.Interval = m_BlinkInterval * 1000
    End Set
End Property
Figure 4 Using an Internal Timer
Public Sub New()
        MyBase.New()

        ' Hook up handler function for timer, and set timer variables

        AddHandler myTimer.Elapsed, AddressOf OnTimerExpired
        myTimer.AutoReset = True
        myTimer.Interval = 1000
        myTimer.Enabled = True

        ' Create brushes used for drawing label text

        m_BlinkOnBrush = New System.Drawing.SolidBrush(Me.ForeColor)
        m_BlinkOffBrush = New System.Drawing.SolidBrush(Me.BackColor)
End Sub

   ' Handler for our control's internal timer. 

Private Sub OnTimerExpired(ByVal Source As Object, 
    ByVal e As System.Timers.ElapsedEventArgs)

        ' Toggle the flag the tells the painting code whether to use the 
        ' BlinkOnColor or the BlinkOff color

        If (m_UseBlinkOnColor = True) Then
            m_UseBlinkOnColor = False
        Else
            m_UseBlinkOnColor = True
        End If

        ' Invalidate the control to force a repaint.

        Me.Invalidate()

        ' Fire the blink event to the control's container, in case it 
        ' cares.

        RaiseEvent BlinkStateChanged(m_UseBlinkOnColor)

    End Sub
Figure 5 Paint Event Handler
Private m_BlinkOnBrush As System.Drawing.SolidBrush
Private m_BlinkOffBrush As System.Drawing.SolidBrush
Private m_UseBlinkOnColor As Boolean = True

' This function gets called when the control needs painting

Protected Overrides Sub OnPaint(ByVal pe As _
System.Windows.Forms.PaintEventArgs)

    Dim BrushToUse As System.Drawing.Brush

    ' Choose the brush to use for the text color. If the blink cycle is
    ' currently on, or if we're in design mode (in which case we never
    ' want to blink, select the first brush. Otherwise select the second.

    If (m_UseBlinkOnColor = True Or Me.DesignMode = True) Then
        BrushToUse = m_BlinkOnBrush
    Else
        BrushToUse = m_BlinkOffBrush
    End If

    ' Draw the control's current Text property

    pe.Graphics.DrawString (Me.Text, Me.Font, BrushToUse, 0, 0)

End Sub
Figure 8 Code of Inherited Control
Public Class InheritTextBoxControl1VB
    Inherits System.Windows.Forms.TextBox    ' Check to see if string in text box appears to be a valid e-mail 
    ' address. In this case, that means that it contains at least one @ 
    ' sign and at least one period.

    Protected Overrides Sub OnTextChanged(ByVal e As System.EventArgs)

        ' Pass call to base class

        MyBase.OnTextChanged(e)

        ' Perform our checking logic using inherited property Text, and
        ' set value of inherited property BackColor accordingly

        If (Me.Text.IndexOf("@") <> -1 And Me.Text.IndexOf(".") <> -1)        
            Then
            Me.BackColor = System.Drawing.Color.LightGreen
        Else
            Me.BackColor = System.Drawing.Color.LightPink
        End If

    End Sub
End Class
Figure 11 Sample User Control
Public Class UserControlVB
    Inherits System.Windows.Forms.UserControl    ' User clicked OK. 

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
        System.EventArgs) Handles Button1.Click

        Dim bFieldsValid As Boolean = True

        ' Check to make sure that required fields are filled in.
        ' Set error provider control to signal errors to the user if 
        ' they're not.

        If (TextBox1.Text.Length = 0) Then
            ErrorProvider1.SetError(TextBox1, "A UserID is required")
            bFieldsValid = False
        Else
            ErrorProvider1.SetError(TextBox1, "")
        End If

        If (TextBox2.Text.Length = 0) Then
            ErrorProvider1.SetError(TextBox2, "A Password is required")
            bFieldsValid = False
        Else
            ErrorProvider1.SetError(TextBox2, "")
        End If

        ' Fire event to container if they are. 

        If (bFieldsValid = True) Then
            RaiseEvent OkClicked(TextBox1.Text, TextBox2.Text)
        End If

    End Sub

    ' User clicked Cancel. Fire event to container.

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button2.Click
        RaiseEvent CancelClicked()
    End Sub

    ' Events that this control fires to its container when the user       
    ' clicks the OK button or the Cancel button.

    Public Event OkClicked(ByVal UserID As String, ByVal Password As _
      String)
    Public Event CancelClicked()

End Class
Page view tracker