Vb.net 订购系统（比萨饼）

我需要帮助创建一个比萨饼订购系统，该系统允许用户通过复选框选择大小和配料，通过数字向上向下选择数量，并允许用户在文本框中输入客户给出的数量，过程是将所选文本框的所有值相加，然后乘以数量，它还计算由于客户引起的变化，输出是在列表框中显示交易（多个）（总价、给定金额和变化）

问题在于，复选框没有添加正确的值，当单击“计算”按钮时，列表框中的值在第一次交易后加倍。以下是我的代码：

    Public Class Form1
Dim small As Double = 25.75
Dim medium As Double = 69.46
Dim large As Double = 98.21
Dim extraCheese As Double = 5.12
Dim mushrooms As Double = 5.75
Dim blackOlives As Double = 5.25
Dim onions As Double = 4.0
Dim greenPepper As Double = 4.5
Dim tomatoes As Double = 4.25
Dim change As Double
Dim total As Double
Dim amountGiven As Double
Dim pizzaSize As Double
Dim pizzaToppings As Double


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


    If (smallCheckbox.Checked) = True Then
        pizzaSize = pizzaSize + small
    End If
    If mediumCheckbox.Checked = True Then
        pizzaSize = pizzaSize + medium
    End If
    If largeCheckbox.Checked = True Then
        pizzaSize = pizzaSize + large
    End If
    If extraCheeseCheckbox.Checked = True Then

        pizzaToppings = pizzaToppings + extraCheese
    End If
    If mushroomsCheckbox.Checked = True Then
        pizzaToppings = pizzaToppings + mushrooms
    End If
    If blackOlivesCheckbox.Checked = True Then
        pizzaToppings = pizzaToppings + blackOlives
    End If
    If onionsCheckbox.Checked = True Then
        pizzaToppings = pizzaToppings + onions
    End If
    If greenPepperCheckbox.Checked = True Then
        pizzaToppings = pizzaToppings + greenPepper
    End If
    If tomatoesCheckbox.Checked = True Then
        pizzaToppings = pizzaToppings + tomatoes

    End If


    total = (pizzaSize + pizzaToppings) * NumericUpDown1.Value
    totalTextbox.Text = total

    amountGiven = TextBox2.Text
    change = amountGiven - total
    TextBox3.Text = change

    ListBox1.Items.Add("==========================================")

    If smallCheckbox.Checked Then
        ListBox1.Items.Add("Pizza size : Small")
    End If
    If mediumCheckbox.Checked Then
        ListBox1.Items.Add("Pizza size : Medium")
    End If
    If largeCheckbox.Checked Then
        ListBox1.Items.Add("Pizza size : Large")
    End If


    ListBox1.Items.Add("Quantity : " & NumericUpDown1.Value)
    ListBox1.Items.Add("Total Cost : " & total.ToString )
    ListBox1.Items.Add("Amount Tendered : " & amountGiven)
    ListBox1.Items.Add("Change : " & change)
    ListBox1.Items.Add("==========================================")
    ListBox1.Items.Add("                                          ")
    ListBox1.Items.Add("==========================================")

End Sub

---

如果有人能帮助我，我将不胜感激。谢谢

您的事务变量永远不会重置为零。试试这个

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

pizzaSize = 0;

---

请更具体地说明它是如何发生故障的。例如，包括您的输入、预期输出和实际输出（或错误）。在开始添加变量之前，您从不初始化变量。这意味着，一旦输入一次并开始一个新的顺序，变量仍然包含上一个顺序末尾的值。