image update

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I'm having problems on drawing an image inside a picturebox. The situation is
this:
I have a picturebox with an image.whenever i click the mouse right button,
another picturebox will appear on top of the first one an will zoom a part of
the image (200px width and 200 px height). It should create the efect of a
magnifying glass
the problem is that when i created the mousedown event, the image appeared
on the picturebox (but i don't know why, it only apeared the secound time the
button was clicked). When i had the picDraw_MouseUp event, the image stoped
apearing, because of the instruction:
picZoom.Visible = False
If i delete the picDraw_MouseUp and start using the picDraw_MouseMo ve event,
the same thing happens. Of course that my intention is to use all the events
listed here, but it seems that after a certain refresh is made to the
picturebox, the image stops apearing.
Does anyone know how to solve this situation? is there any explanation for
this? How can i solve it?
My thanks in advanced
Private Sub picDraw_MouseDo wn(ByVal sender As Object, ByVal e As
System.Windows. Forms.MouseEven tArgs) Handles picDraw.MouseDo wn
picZoom.Visible = True
picZoom.BringTo Front()
If e.X 100 Then
picZoom.Left = e.X - 100
Else
picZoom.Left = e.X
End If
If e.Y 100 Then
picZoom.Top = e.Y - 100
Else
picZoom.Top = e.Y
End If

picZoom.Width = 200
picZoom.Height = 200
picZoom.SizeMod e = PictureBoxSizeM ode.StretchImag e

Dim rectZoom As New Rectangle(picZo om.Left, picZoom.Top, 200, 200)
Dim rectDestino As New Rectangle(0, 0, 200, 200)
Dim grTmp As Graphics = picZoom.CreateG raphics()
Dim imgImagem As Image = picDraw.Image
grTmp.DrawImage (imgImagem, rectDestino, rectZoom, GraphicsUnit.Pi xel)

m_bolZoom = True
End Sub

Private Sub picDraw_MouseMo ve(ByVal sender As Object, ByVal e As
System.Windows. Forms.MouseEven tArgs) Handles picDraw.MouseMo ve
If e.Button.Right And m_bolZoom Then
Dim gt As Graphics = picZoom.CreateG raphics
Dim bmp As New Bitmap(picZoom. Width, picZoom.Height, gt)
If e.X 100 Then
picZoom.Left = e.X - 100
Else
picZoom.Left = e.X
End If
If e.Y 100 Then
picZoom.Top = e.Y - 100
Else
picZoom.Top = e.Y
End If
picZoom.Image = bmp
'picZoom.Refres h()
Debug.Print(pic Zoom.Image.Widt h)
Debug.Print(pic Zoom.Image.Heig ht)
Exit Sub
End If
End Sub
Private Sub picDraw_MouseUp (ByVal sender As Object, ByVal e As
System.Windows. Forms.MouseEven tArgs) Handles picDraw.MouseUp
If m_bolZoom Then
m_bolZoom = False
picZoom.Visible = False
End If
End Sub