如何用VB.NET设计一个计算器，简单点的，就和附件里的那模式

Public Class Form1
    Dim dengyu, yunsuanfu, xiaoshudian, i As Integer, op As String, op1, op2 As Double
   
    Private Sub Button9_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button9.Click
        If TextBox1.Text = "还未输入过任何数!" Or TextBox1.Text = "请输入数!" Or TextBox1.Text = "0" Then
            TextBox1.Text = "1"
        Else
            If dengyu = 0 And yunsuanfu = 0 Then
                TextBox1.Text = TextBox1.Text & "1"
            Else
                TextBox1.Text = "1"
                dengyu = 0
                yunsuanfu = 0
            End If
        End If
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        dengyu = 0
        yunsuanfu = 0
        xiaoshudian = 0
        op = ""
        op1 = 0
        TextBox1.Text = "还未输入过任何数!"
    End Sub
    Private Sub danshuzishuru(ByVal i)
        If TextBox1.Text = "还未输入过任何数!" Or TextBox1.Text = "请输入数!" Or TextBox1.Text = "0" Then
            TextBox1.Text = i
        Else
            If dengyu = 0 And yunsuanfu = 0 Then
                TextBox1.Text = TextBox1.Text & i
            Else
                TextBox1.Text = i
                dengyu = 0
                yunsuanfu = 0
            End If
        End If
    End Sub

    Private Sub Button10_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button10.Click
        danshuzishuru(2)
    End Sub

    Private Sub Button11_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button11.Click
        danshuzishuru(3)
    End Sub

    Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        danshuzishuru(4)
    End Sub

    Private Sub Button6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button6.Click
        danshuzishuru(5)
    End Sub

    Private Sub Button7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button7.Click
        danshuzishuru(6)
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        danshuzishuru(7)
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        danshuzishuru(8)
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        danshuzishuru(9)
    End Sub

    Private Sub Button18_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button18.Click
        End
    End Sub

    Private Sub Button17_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button17.Click
        dengyu = 0
        yunsuanfu = 0
        xiaoshudian = 0
        op = ""
        op1 = 0
        TextBox1.Text = "还未输入过任何数!"
        Label4.Text = "状态正常"
    End Sub

    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        If TextBox1.Text = "还未输入过任何数!" Or TextBox1.Text = "请输入数!" Then
            TextBox1.Text = "请输入数!"
        Else
            If yunsuanfu = 0 Then
                op1 = TextBox1.Text

            Else
                op1 = op1
            End If
            op = "+"
            TextBox1.Text = "+"
            xiaoshudian = 0
            yunsuanfu = 1
        End If
    End Sub

    Private Sub Button8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button8.Click
        If TextBox1.Text = "还未输入过任何数!" Or TextBox1.Text = "请输入数!" Then
            TextBox1.Text = "请输入数!"
        Else
            If yunsuanfu = 0 Then
                op1 = TextBox1.Text

            Else
                op1 = op1
            End If
            op = "-"
            TextBox1.Text = "-"
            xiaoshudian = 0
            yunsuanfu = 1
        End If
    End Sub

    Private Sub Button12_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button12.Click
        If TextBox1.Text = "还未输入过任何数!" Or TextBox1.Text = "请输入数!" Then
            TextBox1.Text = "请输入数!"
        Else
            If yunsuanfu = 0 Then
                op1 = TextBox1.Text

            Else
                op1 = op1
            End If
            op = "*"
            TextBox1.Text = "*"
            xiaoshudian = 0
            yunsuanfu = 1
        End If
    End Sub

    Private Sub Button15_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button15.Click
        If TextBox1.Text = "还未输入过任何数!" Or TextBox1.Text = "请输入数!" Then
            TextBox1.Text = "请输入数!"
        Else
            If yunsuanfu = 0 Then
                op1 = TextBox1.Text

            Else
                op1 = op1
            End If
            op = "/"
            TextBox1.Text = "/"
            xiaoshudian = 0
            yunsuanfu = 1
        End If
    End Sub

    Private Sub Button14_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button14.Click
        If TextBox1.Text = "还未输入过任何数!" Or TextBox1.Text = "请输入数!" Or dengyu = 1 Or yunsuanfu = 1 Then
            TextBox1.Text = "0."
            xiaoshudian = 1
            dengyu = 0
            yunsuanfu = 0
        Else

            If xiaoshudian = 0 Then
                TextBox1.Text = TextBox1.Text & "."
                xiaoshudian = 1
                dengyu = 0
                yunsuanfu = 0
            End If
        End If



    End Sub

    Private Sub Button16_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button16.Click

1:      Select Case op
            Case "+"
                TextBox1.Text = op1 + TextBox1.Text
                dengyu = 1
                xiaoshudian = 0
            Case "-"
                TextBox1.Text = op1 - TextBox1.Text
                dengyu = 1
                xiaoshudian = 0
            Case "*"
                TextBox1.Text = op1 * TextBox1.Text
                dengyu = 1
                xiaoshudian = 0
            Case "/"
                If TextBox1.Text = "0" Or TextBox1.Text = "0." Or TextBox1.Text = "/" Then
                    Label4.Text = "除数不能为0!已经自动清零!"
                    dengyu = 0
                    yunsuanfu = 0
                    xiaoshudian = 0
                    op = ""
                    op1 = 0
                    TextBox1.Text = "还未输入过任何数!"
                Else
                    TextBox1.Text = op1 / TextBox1.Text
                    dengyu = 1
                    xiaoshudian = 0

                End If



        End Select
    End Sub

    Private Sub Button13_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button13.Click
        If TextBox1.Text = "还未输入过任何数!" Or TextBox1.Text = "请输入数!" Or dengyu = 1 Or yunsuanfu = 1 Or TextBox1.Text = "0" Then
            TextBox1.Text = "0"
            dengyu = 0
            yunsuanfu = 0
        Else
            TextBox1.Text = TextBox1.Text & "0"

        End If
    End Sub
End Class

混分可以不？