VB.NET ติด Error เกี่ยวกับ Event Paint ช่วยตอบหน่อยคร่า

Imports System.Drawing.Drawing2D
Imports System.Runtime.InteropServices
Public Class Form1

    Dim bmp As Bitmap
    Dim Blocation As Rectangle
    Dim g As Graphics
    Dim Dragging As Boolean = False
    Dim OffsetX, OffsetY As Integer

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        bmp = New Bitmap(My.Resources.tree1_1)
        bmp.MakeTransparent(Color.White)
        Blocation = New Rectangle(10, 10, bmp.Width, bmp.Height)
        AddHandler Panel2.Paint, AddressOf Panel2_Paint
        AddHandler Panel2.MouseMove, AddressOf Panel2_MouseMove
        AddHandler Panel2.MouseDown, AddressOf Panel2_MouseDown
        AddHandler Panel2.MouseUp, AddressOf Panel2_MouseUp

    End Sub

    Private Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click
        bmp = New Bitmap(My.Resources.tree1_2)
        bmp.MakeTransparent(Color.White)
        Blocation = New Rectangle(30, 30, bmp.Width, bmp.Height)


    End Sub
    Private Sub Panel2_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Panel2.Paint
        e.Graphics.DrawImage(bmp, Blocation)
    End Sub
    Private Sub Panel2_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Panel2.MouseMove
        ' See if we're dragging.
        If (Dragging) Then
            ' We're dragging the image. Move it.
            Blocation.X = e.X + OffsetX
            Blocation.Y = e.Y + OffsetY

            ' Redraw.
            Panel2.Invalidate()
        Else
            ' We're not dragging the image. See if we're over it.
            Dim new_cursor As Cursor = Cursors.Default
            If (PointIsOverPicture(e.X, e.Y)) Then
                new_cursor = Cursors.Hand
            End If
            If (Panel2.Cursor <> new_cursor) Then
                Panel2.Cursor = new_cursor
            End If
        End If
    End Sub

    Private Sub Panel2_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Panel2.MouseDown
        ' See if we're over the picture.
        If (PointIsOverPicture(e.X, e.Y)) Then
            ' Start dragging.
            Dragging = True

            ' Record the offset from the mouse to the picture's origin.
            OffsetX = Blocation.X - e.X
            OffsetY = Blocation.Y - e.Y
        End If
    End Sub

    Private Sub Panel2_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Panel2.MouseUp
        Dragging = False
    End Sub


    Private Function PointIsOverPicture(ByVal x As Integer, ByVal y As Integer) As Boolean
        ' See if it's over the picture's bounding rectangle.
        If ((x < Blocation.Left) OrElse _
            (y < Blocation.Top) OrElse _
            (x >= Blocation.Right) _
            OrElse (y >= Blocation.Bottom)) _
                Then Return False

        ' See if the point is above a non-transparent pixel.
        Dim i As Integer = x - Blocation.X
        Dim j As Integer = y - Blocation.Y
        Return (bmp.GetPixel(i, j).A > 0)
    End Function

End Class