Dynamically changing image in picture box not working - vb.net

Question

I've been trying to figure this out off-and-on for weeks.
In my VB 2010 Forms application, I have a number of picture boxes which are populated with images from other picture boxes using the drag-and-drop method. That's no problem, it works fine. The picture boxes are all in a groupbox container.
The problem is trying to swap images between two picture boxes on a drag-and drop operation. In other words pBox1 has image.x and pBox2 has image.y. Drag the image from pBox2 to pBox1, and drop it; pBox1 will then have image.y from pBox2 and pBox2 will have image.x from pBox1.
With this example, here's the code I have so far:
Private Sub pBox2_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles pBox1.MouseDown
strImageSource = "pBox2" 'strImageSource is a global string variable
[other stuff]
end sub
^ This saves the name of the source picture box to a global string.
Private Sub pBox1_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles pBox1.DragDrop
For Each Control as PictureBox in GroupBox1.Controls.OfType(of PictureBox)()
if Control.Name = strImageSource then
Control.Image = pBox1.Image
end if
next
dim imgTarget as Image = CType((e.Data.GetData(DataFormats.Bitmap)), Bitmap)
pBox1.image = imgTarget
End Sub
^ This searches for the picture box as named by the strImageSource ("pBox2") and copies the contents of pBox1 into it, and then drops the image that was in pBox2 into pBox1.
I hope this makes sense.
This correctly places the image from pBox2 into pBox1, but it does not switch the image from pBox1 into pBox2. pBox2 is just blank. However, debugging shows that the image in pBox2 is not nothing; it does contain a bitmap. It's just not visible.
Now, just as a test, I added a line to the For Each section that would change the background color of the picture box:
For Each Control as PictureBox in GroupBox1.Controls.OfType(of PictureBox)()
if Control.Name = strImageSource then
Control.Image = pBox1.Image
Control.BackColor = color.red
end if
next
And the back color does change. This tells me that the For Each section is working -- it's finding the control and changing the back color. It's just not showing the image.
Is there something I am overlooking?
Thanks!

Answer 1

Instead of using strImageSource, use a global variable defined as a Picturebox
Private tmpPictureBox As PictureBox
Then store that picturebox reference so you can set its image on DragDrop
Private Sub pBox2_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles pBox1.MouseDown
'store the picturebox reference
tmpPictureBox = sender
[other stuff]
end sub
Private Sub pBox1_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles pBox1.DragDrop
'set the first image to the second
tmpPictureBox.Image = sender.image
'set the second image to the first
pBox1.image = CType((e.Data.GetData(DataFormats.Bitmap)), Bitmap)
End Sub

Answer 2

You should call Control.Refresh() on the PictureBox controls in order to update the images.

Answer 3

OK, this was stupid.
I was doing everything right with one really boneheaded exception. In another part of the code, inexplicably, I was clearing the picture boxes of content after the image was replaced. It may have been a remnant of something I was trying to do unrelated to this problem, and I just never corrected it.
My apologies for that, and thanks for all the responses.