Question

 If btnTotalCost.Text = "Calculate total cost" Then

        btnTotalCost.Text = "Refresh"
    Else

        btnTotalCost.Text = "Calculate total cost"
    End If

    Dim dHamSandwich As Decimal = 1.35

    Dim sHamQuantity As Single

    txtHam.Text = sHamQuantity

    dTotalSandwichCost = dHamSandwich * sHamQuantity

    If btnTotalCost.Text = "Refresh" Then
        MsgBox(dTotalSandwichCost)


    End If

当我计算出现的消息框显示数字0.我希望它将数量和成本相乘以得出三明治的总成本。例如，如果我在数量文本框中输入2，则应将1.35乘以2.

Answer 1

首先，您应该完全指定您使用的内容。正如Ste Griffiths的评论所暗示的那样，它似乎是VB.NET。

其次请开始学习数据类型和变量的使用。

你做

Dim dHamSandwich As Decimal = 1.35 ' <- this is fine

Dim sHamQuantity As Single '<- this is an uninitialised Single variable, in .net it will be set to 0

txtHam.Text = sHamQuantity '<- then you assign the unassigned Single variable to your Textbox's property Text(which requires a string)  
'That means it will implicitly convert the Single to String and then "show" it in the textbox (which will be 0)

dTotalSandwichCost = dHamSandwich * sHamQuantity 'here you multiply 1.35 * 0. Sure it will be 0. Also you multiply a decimal with a single data type which will implicitly convert the latter (if I remember correctly)

这里的问题是。为什么你甚至使用Single和Decimal？你可以使用任何一个。但主要问题实际上甚至不是数据类型，而是赋值。

乘以单数和小数

1 个答案: