Question regarding images and winforms

Question

I am creating a Kiosk application. I have it full screen and I am drawing directly on the form:

Private Function CreateHeader(ByVal headerText As String) As Boolean
    Try
        Dim oGFX As Graphics = Graphics.FromHwnd(hwnd:=_oP.Handle)
        Dim oRect As Rectangle = New Rectangle(x:=0, y:=0, Width:=_screenSize.X, Height:=150)
        Dim oBMP As New Bitmap(GetEmbeddedResourceStream("Kiosk.logo.jpg"))

        Dim oBrush As Brush = New SolidBrush(Color.FromArgb(red:=0, green:=0, blue:=153))


        oGFX.FillRectangle(brush:=oBrush, rect:=oRect)
        oGFX.DrawImage(image:=oBMP, _
                           x:=0, _ 
                           y:=0, _
                       width:=oBMP.Width, _ 
                      height:=oBMP.Height)

        If Not String.IsNullOrEmpty(headerText) Then
            Dim oFont As New Font("Impact", 48, FontStyle.Regular)
            Dim g As Graphics = Me.CreateGraphics()

            Dim oStringSize As SizeF = g.MeasureString(headerText, oFont)

            g = Nothing

            oGFX.DrawString(s:=headerText, _
                         font:=oFont, _
                        brush:=Brushes.White, _
                            x:=(oRect.Width - Math.Round(oStringSize.Width, 0)) / 2, _
                            y:=(oRect.Height - Math.Round(oStringSize.Height, 0)) / 2)
        End If

        Return True
    Catch ex As Exception
        Return False
    End Try
End Function

Everything draws fine, but the second I press Alt or Tab (individually or together, in any order) the rectangle I drew disappears. If I call the function again, it redraws and stays no matter what button I press. Is there some sort of .NET function that I need to call so my drawing function only needs to be called once?

Thanks.

Answer 1

You should be doing your painting by overriding OnPaint - then you will be able to re-paint as necessary. At the moment, anything you draw is only valid under the screen is invalidated.