Entering Picturebox control with mouse down - vb.net

Question

I'm writing a "quick 'n dirty" image editor. The user can load an image into pbOriginal, drag a cropping square in it, and have it displayed in pbAltered. The functionality works well for my purposes.
However I'm having problems coding when the user mouses into the picturebox with the mouse button down. (Kind of like a drag event, but I'm not trying to drag anything in; I just want to capture the enter with the mouse down.) Ideally I'd like to have it start the selection process as soon as it detects entry and detects the active LMB, but nothing I've thrown at it so far seems to work.
Here are two code snippets I have. The first detects the MouseDown event, the second detects the MouseMove event. I'm looking to have something mimicking the actions of the MouseDown function with MouseEnter. (The second function is irrelevant, but I'm including it for the sake of completeness.)
Private Sub pbOriginal_MouseDown(sender As Object, e As MouseEventArgs) Handles pbOriginal.MouseDown
If e.Button = Windows.Forms.MouseButtons.Left Then
cropX = e.X
cropY = e.Y
cropPen = New Pen(Color.Red, 2)
cropPen.DashStyle = DashStyle.DashDotDot
Altered = Nothing
End If
pbOriginal.Refresh()
End Sub
Private Sub pbOriginal_MouseMove(sender As Object, e As MouseEventArgs) Handles pbOriginal.MouseMove
Cursor = Cursors.Cross
If pbOriginal.Image Is Nothing Then Exit Sub
If cropX < 0 Or cropY < 0 Then Exit Sub
If e.Button = Windows.Forms.MouseButtons.Left And e.X <= pbOriginal.Right - pbOriginal.Left And e.X >= 0 And e.Y <= pbOriginal.Bottom - pbOriginal.Top And e.Y >= 0 Then
pbOriginal.Refresh()
Dim OldWidth As Integer = cropWidth
Dim OldHeight As Integer = cropHeight
cropWidth = e.X - cropX
cropHeight = e.Y - cropY
'Verify that we're maintaining a square
If cropWidth > cropHeight Then
If cropWidth > OldWidth Then
cropWidth = cropHeight
Else
cropHeight = cropWidth
End If
End If
If cropHeight > cropWidth Then
If cropHeight > OldHeight Then
cropHeight = cropWidth
Else
cropWidth = cropHeight
End If
End If
If cropWidth <= 0 Or cropHeight <= 0 Then
Altered = Nothing
btnCropNext.Enabled = False
Exit Sub
End If
pbOriginal.CreateGraphics.DrawRectangle(cropPen, cropX, cropY, cropWidth, cropHeight)
If cropWidth <> 0 And cropHeight <> 0 Then
Dim WRatio As Double = Original.Width / pbOriginal.Width
Dim HRatio As Double = Original.Height / pbOriginal.Height
Dim rect As Rectangle = New Rectangle(cropX * WRatio, cropY * HRatio, cropWidth * WRatio, cropHeight * HRatio)
'First we define a rectangle with the help of already calculated points
Dim OriginalImage As Bitmap = New Bitmap(Original, Original.Width, Original.Height)
'Original image
Dim _img As New Bitmap(CInt(cropWidth * WRatio), CInt(cropHeight * HRatio)) ' for cropinf image
Dim g As Graphics = Graphics.FromImage(_img) ' create graphics
g.InterpolationMode = Drawing2D.InterpolationMode.HighQualityBicubic
g.PixelOffsetMode = Drawing2D.PixelOffsetMode.Default
g.CompositingQuality = Drawing2D.CompositingQuality.HighQuality
'set image attributes
g.DrawImage(OriginalImage, 0, 0, rect, GraphicsUnit.Pixel)
Altered = _img
btnCropNext.Enabled = True
OriginalImage.Dispose()
Else
Altered = Nothing
btnCropNext.Enabled = False
End If
End If
End Sub

Answer 1

Why dont you use MouseEnter Event , and test if the LMB if its clicked, if so make your selection progress, other wise neglect.
More Info About MouseEnter
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.mouseenter(v=vs.110).aspx
if you dont want to use MouseEnter , in MouseMove test each picture if MouseOver and the LMB . but i think the first easier and faster to handle