Imports System.Drawing.Drawing2D
Public Class Form1
    Dim bzpoints() As Point = {New Point(50, 400), New Point(250, 400), New _
      Point(400, 400), New Point(450, 100)}
    Dim gpath As New GraphicsPath
    Dim curpoint As Int32
    Dim ptsvisible As Boolean
    Private Sub Form1_MouseDown(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
        curpoint = -1
        If ptsvisible AndAlso gpath.IsVisible(e.Location) Then
            For i As Int32 = 0 To 3
                If Math.Abs(e.X - bzpoints(i).X) < 6 AndAlso Math.Abs(e.Y - _
                  bzpoints(i).Y) < 6 Then
                    curpoint = i
                End If
            Next
        End If
        If e.Button = Windows.Forms.MouseButtons.Right Then
            ptsvisible = Not ptsvisible
            Me.Refresh()
        End If
    End Sub
    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint
        e.Graphics.SmoothingMode = SmoothingMode.HighQuality
        e.Graphics.DrawBezier(New Pen(Color.Yellow, 2), bzpoints(0), bzpoints( _
          1), bzpoints(2), bzpoints(3))
        If ptsvisible Then
            gpath.Reset()
            For i As Int32 = 0 To 3
                gpath.AddEllipse(bzpoints(i).X - 5, bzpoints(i).Y - 5, 10, 10)
            Next
            e.Graphics.FillPath(Brushes.Red, gpath)
        End If
    End Sub
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        Me.SetStyle(ControlStyles.DoubleBuffer Or ControlStyles.UserPaint Or _
        ControlStyles.AllPaintingInWmPaint, True)
        Me.SetBounds(100, 100, 500, 500)
        Me.BackColor = Color.Black
    End Sub
    Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove
        If ptsvisible AndAlso curpoint > -1 AndAlso e.Button = _
        Windows.Forms.MouseButtons.Left Then
            bzpoints(curpoint) = New Point(e.X, e.Y)
            Me.Refresh()
        End If
    End Sub
End Class