Question

我有一个简单的程序，但是我不能让这个类返回一个矩形的区域;它总是返回0，包括类的变量。对于我的生活，我无法让这件事工作。这是主要形式：

Public Class Form1

Private Sub btnCalc_Click(sender As Object, e As EventArgs) Handles btnCalc.Click
    Dim rect As New Rectangle
    'Dim strLength As String
    'Dim strWidth As String

    Double.TryParse(txtLength.Text, rect.Length)
    Double.TryParse(txtWidth.Text, rect.Width)

    'strLength = InputBox("Please input the length of the rectangle", "Calculate Area")
    'Double.TryParse(strLength, rect.Length)
    'strWidth = InputBox("Please input the width of the rectangle", "Calculate Area")
    'Double.TryParse(strWidth, rect.Width)

    lblArea.Text = rect.GetArea.ToString

End Sub
End Class

这是班级

Public Class Rectangle
Private _dblLength As Double
Private _dblWidth As Double

Public Property Length As Double
    Get
        Return _dblLength
    End Get
    Set(value As Double)
        If value > 0 Then
            _dblLength = value
        Else
            _dblLength = 0
        End If
    End Set
End Property

Public Property Width As Double
    Get
        Return _dblWidth
    End Get
    Set(value As Double)
        If value > 0 Then
            _dblLength = value
        Else
            _dblLength = 0
        End If
    End Set
End Property

'when you call New in main form it initalizes the variables
Public Sub New()
    _dblLength = 0
    _dblWidth = 0
End Sub

Public Function GetArea() As Double
    Return _dblLength * _dblWidth
End Function
End Class

Answer 1

您的Width媒体资源出现错误：设置_dblLength，但返回_dblWidth。

_dblWidth将始终为零，因此您的计算区域将始终为零。

用户定义的类始终返回0

1 个答案: