Solution for PrintForm in .NET

[sokkmees]

Hello!

I just found a code snippet that is capable of getting control image even when the control is invisible or overlapped by others

So forget about BitBlt problems

    Private Function GetControlBitmap(ByVal CTL As Control) As Bitmap
        Dim Methods() As System.Reflection.MethodInfo = ctl.GetType.GetMethods( _
            System.Reflection.BindingFlags.Instance Or _
            System.Reflection.BindingFlags.NonPublic)
        Dim i As Integer
        Dim OnPaintMethod As System.Reflection.MethodInfo

        For i = 0 To Methods.Length - 1
            If Methods(i).Name = "OnPaint" Then
                OnPaintMethod = Methods(i)
                Exit For
            End If
        Next

        If Not OnPaintMethod Is Nothing Then
            Dim _BMP As New Bitmap(CTL.Width, CTL.Height)
            Dim _Gr As Graphics = Graphics.FromImage(_BMP)
            Dim PaintEventArgs As New System.Windows.Forms.PaintEventArgs(_Gr, _
            New Rectangle(0, 0, CTL.Width, CTL.Height))
            OnPaintMethod.Invoke(ctl, New Object() {PaintEventArgs})
            _Gr.Dispose()
            Return _BMP
        End If
    End Function

Originally posted in MS VB.NET newsgroup by Craig Vick

[RealisticGraphics]

What's the address to that newsgroup?

[pax]

Pretty Cool

Except, it can't do combo's and listview's and other controls of that nature.

You wouldn't happen to have a fix for that?

[sokkmees]

Address of the newsgroup (taken from Google) is
microsoft.public.dotnet.languages.vb

I'm afraid other controls still have to be drawn from code with simple drawstring, etc functions. At least at the moment I don't know the other way

But this code helped me when I was stuck printing invisible control that does custom drawing under OnPaint event

[RealisticGraphics]

Thanks.

[angrycoder]

ok, I'm new to vb but not programming, but i'm also an idiot.

whenever i call this method from inside a PrintPage event and pass it the Form as the control it wants(casted or not), I use the bitmap it returns and it's always blank. Any idea why? or maybe I'm using it wrong.

I used the BitBlt way, and it captures the GDI+ lines, etc. that I already have drawn on the form, but it also captures things on top of the form, like the stupid "generating preview" dialog box or sometimes taskbar.

arrrgh, i just want to print whats on the form. this "screenshot" way, or variants of it, seem to be the only way to do it too.

[pax]

Angrycoder: You need to do the screenshot and save it in a variable before opening the printpreview.
It sounds like you grab it in the PrintPage event or something.

[sokkmees]

Angrycoder: you have to pass every control on the form one-by-one. It then gives you bitmap that this control draws under its OnPaint event.

[angrycoder]

yeah, I have a form with no controls on it, only stuff drawn on it with GDI+. So I took pax's advice and used the BitBlt way and it works. Thanks guys.

[sokkmees]

Sure BitBlt is the easiest way if you have visible form

[angrycoder]

I thought this way would be better though, since I'm trying to correctly scale it to a sheet of paper (and handling all screen resolutions, bleh). even resizing the bitmap by interpolating and using antialiasing it still looks a bit grainy. but if I use this way and pass the form as the control i want to become a bitmap, it seems to ignore lines i've drawn on it, and returns a blank bitmap