如何创建3个操作数计算器

如何解决如何创建3个操作数计算器

我正在做一个计算器项目，用2个操作数完成，但是努力编写代码并求解3个操作数calc。问题是当我这样做时，例如10 + 10 =（答案20）工作正常，但10 + 10 + 10 =（也答案20）。似乎忘记了第一个变量。

以下是我在vb2010上的代码，请告知我是否错过了什么。谢谢。

Dim first As Double
Dim second As Double
Dim third As Double
Dim answer As Double
Dim process As String

Private Sub Button15_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button15.Click
    first = Val(TextBox1.Text)
    TextBox1.Text = ""
    formula.Text = first & "x"
    process = "*"
End Sub

Private Sub Button14_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button14.Click
    first = Val(TextBox1.Text)
    TextBox1.Text = ""
    formula.Text = first & "+"
    process = "+"
End Sub

Private Sub Button12_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button12.Click
    first = "0"
    second = "0"
    answer = "0"
    formula.Text = ""
    TextBox1.Text = ""

End Sub

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

    If process = "+" Then
        second = Val(TextBox1.Text)
        formula.Text = first & "+" & second & "="
        answer = first + second
        TextBox1.Text = answer
    End If
    If process = "*" Then
        second = Val(TextBox1.Text)
        formula.Text = first & "x" & second & "="
        answer = first * second
        TextBox1.Text = answer
    End If
    If process = "/" Then
        second = Val(TextBox1.Text)
        formula.Text = first & "÷" & second & "="
        answer = first / second
        TextBox1.Text = answer
    End If

    If process = "-" Then
        second = Val(TextBox1.Text)
        formula.Text = first & "-" & second & "="
        answer = first - second
        TextBox1.Text = ""
    End If
   
End Sub


Private Sub Button2_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button2.Click
    first = Val(TextBox1.Text)
    TextBox1.Text = ""
    formula.Text = first & "-"
    process = "-"
End Sub

Private Sub Button1_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles Button1.Click
    first = Val(TextBox1.Text)
    TextBox1.Text = ""
    formula.Text = first & "÷"
    process = "/"
End Sub