Marking madatory textboxes/fields with style

Now everyone in VS2003/2005 who likes graphics has done some code in the onPaint event to draw nice little things, but have you ever tried drawing on a textbox, or any other control for that matter. Wemay also be tired of just filling madatory fields with a plain backcolor fill also. So what I set out to do was draw a nice little glyph in the corner to signify that a filed was mandatory

First off we must subclass the good old textbox, but hopefully you aer doing this already in your component lib. Next it's a matter of hooking up to the windows message and drawing accordingly.

Public Class Component1
    Inherits TextBox
    Private Const WM_PAINT As Integer = &HF

    Private bMandatory

    Public Property Mandatory() As Boolean
        Get
            Return bMandatory
        End Get
        Set(ByVal value As Boolean)
            bMandatory = value
            Me.Invalidate()
        End Set
    End Property

    Protected Overrides Sub WndProc(ByRef m As Message)
        Try
            MyBase.WndProc(m)
            If m.Msg = WM_PAINT And bMandatory Then
                Dim g As Graphics = Me.CreateGraphics
                Dim pts As PointF() = {New PointF(0, 0), New PointF(5, 0), _
                New PointF(0, 5)}
                g.FillPolygon(Brushes.Red, pts)
            End If
        Catch ex As Exception
            ' Call error handler
        End Try

    End Sub

End Class

You should end up with this ...