vb.net 画曲线

Public Class Form1
    Public Enum Type
        None = 0
        Line = 1
        Cirle = 2
        PolyLine = 3
        Curve = 4
    End Enum
    Dim m_Type As Type = Type.None
    Dim First As Point
    Dim Last As Point

    Dim g As Graphics
    Dim listPoint As New List(Of Point)
    Private Sub Initial(sender As Object, e As EventArgs) Handles Button1.Click, Button2.Click, Button3.Click, Button4.Click, MyBase.Load
        m_Type = Type.None
        First = Point.Empty
        Last = Point.Empty

        Dim c As Control = TryCast(sender, Control)

        If IsNothing(c) Then Exit Sub

        Select Case c.Name
            Case "Button1"
                m_Type = Type.Line
            Case "Button2"
                m_Type = Type.Cirle
            Case "Button3"
                m_Type = Type.PolyLine
            Case "Button4"
                m_Type = Type.Curve
        End Select

    End Sub

    Private Sub Form1_MouseClick(sender As Object, e As MouseEventArgs) Handles MyBase.MouseClick
        Dim pen As Pen = New Pen(Color.Red)
        g = Me.CreateGraphics()
        If e.Button = MouseButtons.Left Then
            '分情况
            Select Case m_Type
                Case Type.None
                    Return
                Case Type.Line
                    If First = Point.Empty Then
                        First = New Point(e.X, e.Y)
                    Else
                        Last = New Point(e.X, e.Y)
                        g.DrawLine(pen, First, Last)
                        Me.Initial(Nothing, e) '取消
                    End If
                Case Type.Cirle
                    If First = Point.Empty Then
                        First = New Point(e.X, e.Y)
                    Else
                        Dim R As Integer = Math.Sqrt((First.X - e.X) * (First.X - e.X) + (First.Y - e.Y) * (First.Y - e.Y))
                        Dim left As New Point(First.X - R, First.Y - R)
                        g.DrawEllipse(pen, left.X, left.Y, 2 * R, 2 * R)
                        Me.Initial(Nothing, e) '取消
                    End If
                Case Type.PolyLine
                    If First = Point.Empty Then
                        First = New Point(e.X, e.Y)
                    Else
                        Last = New Point(e.X, e.Y)
                        g.DrawLine(pen, First, Last)
                        First = Last
                    End If

                Case Type.Curve
                    If First = Point.Empty Then
                        First = New Point(e.X, e.Y)
                        listPoint.Add(First)
                    Else
                        Last = New Point(e.X, e.Y)
                        listPoint.Add(Last)
                        If Type.Curve = m_Type Then
                            If listPoint.Count = 3 Then
                                g.DrawCurve(pen, listPoint.ToArray(), 0.5)
                            End If
                        End If
                    End If
            End Select
        ElseIf e.Button = MouseButtons.Right Then

            Me.Initial(Nothing, e) '取消
        End If
    End Sub


End Class