Late Binding Error on CreateGraphics in DLL

Question

I have a DLL that is a very basic image management library.  To draw graphics I am using the following subroutine:
Public Sub DrawImage(ByVal Surface As Object, ByVal Name As String, ByVal Position As Point, Optional Size As Point = Nothing)
            Try
                If Images.ContainsKey(Name) Then
                    Dim g As Graphics = Surface.CreateGraphics
                    If Size.IsEmpty Then
                        g.DrawImage(Images(Name), Position)
                    Else
                        g.DrawImage(Images(Name), New Rectangle(Position.X, Position.Y, Size.X, Size.Y))
                    End If
                End If
            Catch ex As Exception
                MsgBox(ex.ToString)
            End Try
        End Sub
Object passed as the surface is a PictureBox on the main form so that the image is drawn in the PictureBox.  It all works perfectly except when I try to use Option Strict On (which is my preference) in the DLL.  When I do this the Surface.CreateGraphics
line gives me a late binding error.  I am very new to coding and have not been able to figure out a solution.  When similar errors have occurred I have been able to use DirectCast() to remove the error.  For my current situation I do not know
how to apply the cast, if it is even possible.  Any help or suggestions?

Answer 1

Hi,
 You should be doing this one of two ways. One is to declare Surface as a Graphics type in the sub like below. This is the way i would recommend doing it.
 You will also notice that the last parameter is not Optional any more and is renamed to something other than Size and is changed to a Size Type. The name Size is the name of the Drawing Size structure so you need to use a different name. Also because
an Optional parameter is not able to use a Structure type which Size is, it can`t be Optional.
 You will also notice i changed the name of your sub to DrawMyImage. You really need to choose names that are not used for Classes, properties, and methods already. The DrawImage name is already used by the Graphics class.
    Public Sub DrawMyImage(ByVal Surface As Graphics, ByVal Name As String, ByVal Position As Point, ByVal DrawSize As Size)
        Try
            If Images.ContainsKey(Name) Then
                'Dim g As Graphics = Surface.CreateGraphics
                If Size.IsEmpty Then
                    Surface.DrawImage(Images(Name), Position)
                Else
                    Surface.DrawImage(Images(Name), New Rectangle(Position.X, Position.Y, DrawSize.Width, DrawSize.Height))
                End If
            End If
        Catch ex As Exception
            MsgBox(ex.ToString)
        End Try
    End Sub
 Then call your Function from within the PictureBox`s Paint event in the Form like this
Public Class Form1
Private DrawingClass As New NameOfYourClass
Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
Dim SomeLocation As New Point(10, 10)
Dim SomeSize As New Size(100, 90)
DrawingClass.DrawMyImage(e.Graphics, "Some Image Name", SomeLocation, SomeSize)
End Sub
End Class
 The other way would be to make the Surface parameter a PictureBox type and pass the PictureBox to the sub. I would also recommend not using the CreateGraphics method. If you really must do it like this then at least creat the graphics
in a Using End Using block. A Graphics Object needs to be Disposed when you are done using it and this will take care of that for you.
Public Sub DrawMyImage(ByVal Surface As PictureBox, ByVal Name As String, ByVal Position As Point, ByVal DrawSize As Size)
Try
If Images.ContainsKey(Name) Then
Using g As Graphics = Graphics.FromHwnd(Surface.Handle)
If Size.IsEmpty Then
g.DrawImage(Images(Name), Position)
Else
g.DrawImage(Images(Name), New Rectangle(Position.X, Position.Y, DrawSize.Width, DrawSize.Height))
End If
End Using
End If
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
 Then you can call your sub from other places in the form than the Paint event like this. However, this will not be persistent doing it like this. Meaning if you draw the image and then move the form off the side of the screen, cover it with another form,
or minimize it the image will be erased and not be redrawn again until you call the sub again.
Public Class Form1
Private DrawingClass As New NameOfYourClass
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim SomeLocation As New Point(10, 10)
Dim SomeSize As New Size(100, 90)
DrawingClass.DrawImage(PictureBox1, "Some Image Name", SomeLocation, SomeSize)
End Sub
End Class
If you say it can`t be done then i`ll try it