Custom ComboBox loses animation effect.

Hey all, i tried to create a custom combobox with borders and some additional things to make it look more modern. Here is the code of the paint method i call inside OnPaint

Code:

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Public Sub CustomPaint(screenGraphics As Graphics)
        ' If there is body to be drawn.
        If Me.Width > 0 AndAlso Me.Height > 0 Then
            ' Clear the background image graphics
            If Me.m_backImage Is Nothing Then
                '        Cached Background Image
                Me.m_backImage = New Bitmap(Me.Width, Me.Height)
                Dim backGraphics As Graphics = Graphics.FromImage(Me.m_backImage)
                backGraphics.Clear(Color.Transparent)
                Me.PaintTransparentBackground(backGraphics, Me.ClientRectangle)
            End If

            m_BackGraphics.Clear(Color.Transparent)
            m_BackGraphics.DrawImageUnscaled(Me.m_backImage, 0, 0)

            m_ControlGraphics.Clear(Color.Transparent)
            m_ControlGraphics.SmoothingMode = SmoothingMode.HighQuality
            'm_ControlGraphics.Clip = New Region(GetBoxBorder())

            ' Begin drawing
            'Calculate the current dropdown rectangle
            DropDownRectangle = New Rectangle(Bounds.Right - SplitSectionWidth, 0, SplitSectionWidth, Bounds.Height)

            Using pen As Pen = New Pen(Color.Black)
                m_ControlGraphics.DrawPath(pen, GetBoxBorder())
                PaintArrowAndLine(m_ControlGraphics)
            End Using

            m_ControlGraphics.Flush()

            m_BackGraphics.DrawImage(m_ControlBuffer,
                                        New Rectangle(0, 0,
                                                      m_ControlBuffer.Width,
                                                      m_ControlBuffer.Height),
                                        0, 0,
                                        m_ControlBuffer.Width,
                                        m_ControlBuffer.Height,
                                        GraphicsUnit.Pixel)
            m_BackGraphics.Flush()

            '        Now paint this to the screen
            screenGraphics.DrawImageUnscaled(m_BackBuffer, 0, 0)
        End If
    End Sub

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and here is the code for de DrawItem method,

Code:

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Protected Overrides Sub OnDrawItem(e As DrawItemEventArgs)
        Dim brush As SolidBrush = New SolidBrush(Color.LightGray)
        e.Graphics.SmoothingMode = SmoothingMode.HighQuality

        If e.Index < 0 Then Exit Sub

        Dim rect As Rectangle = e.Bounds
        Dim TextBrush As Brush
        Dim index As Integer = If(e.Index >= 0, e.Index, 0)

        If e.State And DrawItemState.Selected Then
            'selection background color
            e.Graphics.FillRectangle(brush, rect)
            'selection forecolor
            TextBrush = Brushes.White
            e.Graphics.DrawString(Me.Items(index).ToString(), e.Font, TextBrush, e.Bounds, StringFormat.GenericDefault)
        Else
            e.Graphics.FillRectangle(Brushes.White, rect)
            TextBrush = Brushes.Black
            e.Graphics.DrawString(Me.Items(index).ToString(), e.Font, TextBrush, e.Bounds, StringFormat.GenericDefault)
        End If

        MyBase.OnDrawItem(e)
    End Sub

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My problem is that i lose the animation it makes when displaying the items. I should note that when used isolated the animation works great, but when in some other VS projects it stops working. The items appear suddenly, with no sliding.
Any recommendations?