Question

我正在上大学的IT课程，其中一项任务要求您使用面向对象的技术在Visual Basic中创建一个BMI计算器。我不是一个很好的程序员，因此我一直困扰着我不断收到的问题。我使用的代码是由声称可以使用的人提供给我的，但是当我运行该程序时，给出的任何结果都是NaN。

为了给我这个结果，任何人都知道代码有什么问题吗？

这是我正在使用的代码：

Public Class Form1
Private Sub Button_Calculate_Click(sender As Object, e As EventArgs) Handles 
Button_Calculate.Click
    Dim height As Double = Double.Parse(TextBox_Height.Text)
    Dim weight As Double = Double.Parse(TextBox_Weight.Text)


    bmi.SetWeight(weight)
    bmi.SetHeight(height)

    TextBox_BMI.Text = Format(bmi.GetBMI(), "0.00")
End Sub

Private bmi As New BMI
End Class

在单独的班级：

Public Class BMI
Public Function GetBMI()
    Return (weight / (height ^ 2))
End Function

Public Function GetWeight()
    Return weight
End Function
Public Function GetHeight()
    Return height
End Function

Public Function SetWeight(_weight As Double)
    Return weight = _weight
End Function
Public Function SetHeight(_height As Double)
    Return height = _height
End Function

Private weight As Double
Private height As Double
End Class

Answer 1

您的（意思是kushlord420）解决方案存在一些问题。

Visual Basic代码不区分大小写，因此bmi与BMI相同
您永远不会使用Form级别变量bmi，因此请删除。
您尝试编写自定义构造函数，但在vb.net中它是Sub New
您要将体重和身高文本框中的值转换为Double，但是属性的类型为Single。其实这应该是Single.TryParse，但这又是一天。
vb.net中的函数必须具有返回值的数据类型。在函数的第一行中提供了此功能。既然你是在返回值上使用Format我将值设为String，转换了返回值。
修复了构造函数参数，以避免产生歧义。

    Sub Button_Calculate_Click(sender As Object, e As EventArgs) Handles Button_Calculate.Click
        Dim bmi As New BMI(CSng(TextBox_Weight.Text), CSng(TextBox_Height.Text))
        TextBox_BMI.Text = Format(bmi.GetBMI(), "0.00")
    End Sub

    Public Class BMI
        Public Function GetBMI() As String
            Return (Weight / (Height ^ 2)).ToString
        End Function

        Public Property Weight As Single
        Public Property Height As Single

        Public Sub New(wght As Single, hght As Single)
            Weight = wght
            Height = hght
        End Sub
    End Class

Answer 2

您确实需要更多类似这样的东西：

Public Class BMI
    Public Function GetBMI() As Double
        Return (weight / (height ^ 2))
    End Function

    Public Property Weight As Double
    Public Property Height As Double

    Public Sub New(weight As Double, height As Double)
        Me.Weight = weight
        Me.Height = height
    End Sub
End Class

Public Class Form1
    Private Sub Button_Calculate_Click(sender As Object, e As EventArgs) Handles Button_Calculate.Click
        Dim bmi As New BMI(CDbl(TextBox_Weight.Text), CDbl(TextBox_Height.Text))
        TextBox_BMI.Text = Format(bmi.GetBMI(), "0.00")
    End Sub
End Class

或者更好的是，

Public Class BMI

    Public Property Weight As Double
    Public Property Height As Double

    Public ReadOnly Property BMI As Double
        Get
            Return (Weight / (Height ^ 2))
        End Get
    End Property

    Public Sub New()
    End Sub

    Public Sub New(weight As Double, height As Double)
        Me.Weight = weight
        Me.Height = height
    End Sub
End Class

Answer 3

在朋友的帮助下，找出了我的问题。

如果有人好奇，请使用以下代码：

Public Class Form1
 Sub Button_Calculate_Click(sender As Object, e As EventArgs) Handles 
Button_Calculate.Click
  Dim bmi As New BMI With {.Weight = CDbl(TextBox_Weight.Text), .Height = 
  CDbl(TextBox_Height.Text)}
  TextBox_BMI.Text = Format(bmi.GetBMI(), "0.00")
End Sub


Private bmi As New BMI
End Class

并且：

Public Class BMI
Public Function GetBMI()
    Return (weight / (height ^ 2))
End Function

Property Weight As Single
Property Height As Single

Public Sub BMI(weight As Single, height As Single)
    Me.Weight = weight
    Me.Height = height
End Sub
End Class

Visual Basic BMI计算器给出NaN结果

3 个答案: