Question

我得到了另一个超级基本问题，我试图总计用户输入的txtPrice.Text中每个条目的小计，然后使用更新的税，运费和总计刷新其他标签。它不总是subTotal，其他一切正常。那是怎么回事？

Private Sub btnCalc_Click(sender As Object, e As EventArgs) Handles btnCalc.Click
    Dim sglSub As Single
    Dim sglTotal As Single
    Dim sglSalesTax As Single
    Const TAX_RATE As Single = 0.02
    Dim bytShippingCharge As SByte = 10
    Dim sglCompTotal As Single


    Single.TryParse(txtPrice.Text, sglSub)
    sglTotal += sglSub
    lblSubTotal.Text = sglTotal.ToString("C2")

    sglSalesTax = (sglTotal * TAX_RATE)

    lblTax.Text = sglSalesTax.ToString("C2")

    If sglTotal >= 100 Then
        bytShippingCharge = 0
    End If
    lblShipping.Text = bytShippingCharge.ToString("C2")
    sglCompTotal = (sglTotal + sglSalesTax + bytShippingCharge)
    lblTotal.Text = sglCompTotal.ToString("C2")
End Sub

Answer 1

提示在这一行：

sglTotal += sglSub

- 每次使用总计时，在向其添加值之前将其初始化为零。否则会导致不良后果。

- 使用货币时最好使用小数类型。

如果你想让变量保持其值，则声明它是共享的。

这是一个如何使用共享字段的小例子

Public Class Form1
   Shared total As Decimal = 0D

   Shared Sub calc()
       total += 2
   End Sub


   Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
       calc()
       Label1.Text = total.ToString
   End Sub
End Class

文本框中的多个输入不是总计

1 个答案: