Public Class Form1
 
    Private ptStart As Point
    Private ptEnd As Point
    Private rect As Rectangle
 
    Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        If e.Button = Windows.Forms.MouseButtons.Left Then
            PictureBox1.Refresh()
            ptStart.X = e.X
            ptStart.Y = e.Y
        End If
    End Sub
 
    Private Sub PictureBox1_MouseMove(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
        If e.Button = Windows.Forms.MouseButtons.Left Then
            Dim g As Graphics = PictureBox1.CreateGraphics()
            Dim pen As New Pen(Color.Black, 1)
            PictureBox1.Refresh()
            ptEnd.X = e.X
            ptEnd.Y = e.Y
            rect = New Rectangle(ptStart.X, ptStart.Y, e.X - ptStart.X, e.Y - _
              ptStart.Y)
            Pen.DashStyle = Drawing2D.DashStyle.DashDot
            g.DrawRectangle(pen, rect)
        End If
    End Sub
 
    Private Sub PictureBox1_MouseUp(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseUp
        PictureBox2.Image = GetPicturePart(PictureBox1.Image, rect)
    End Sub
 
    Public Function GetPicturePart(ByVal SourceImage As Image, ByVal Region As _
      Rectangle) As Bitmap
        Dim ImagePart As Bitmap = New Bitmap(Region.Width, Region.Height)
        Using G As Graphics = Graphics.FromImage(ImagePart)
            Dim TargetRect As Rectangle = New Rectangle(0, 0, Region.Width, _
              Region.Height)
            Dim SourceRect As Rectangle = Region
            G.DrawImage(SourceImage, TargetRect, SourceRect, GraphicsUnit.Pixel)
        End Using
        Return ImagePart
    End Function
 
    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) _
      Handles Me.Load
        PictureBox2.SizeMode = PictureBoxSizeMode.AutoSize
    End Sub
End Class