vb.net - 如何在父类中使用子类的值？网络

Question

我有一个令我沮丧不已的问题，我在父类中有一个可重写的函数，在子类中有一个重写函数，如下所示:

子类

Public Overrides Sub UpdatePrice(ByVal dblRetailPrice As Double)
    If dblWholesalePrice < 0 Then
        MessageBox.Show("Error, amount must be greater than 0.")
    Else
        dblRetailPrice = dblWholesalePrice * dblStandardMargin
    End If
End Sub

在父类中，我有

Public ReadOnly Property RetailPrice() As Double
    Get
        Return dblRetailPrice
    End Get
End Property

Public Overridable Sub UpdatePrice(ByVal dblRetailPrice As Double)
    If dblWholesalePrice < 0 Then
        MessageBox.Show("Please input an amount greater than 0,wholesale price has not changed", "error")
    Else
        dblRetailPrice = 1.1 * dblWholesalePrice
    End If
End Sub

当我调试时，产生了值，但它没有传递给 ski.RetailPrice() 的父类，这里似乎有什么问题？任何帮助将不胜感激。

Answer 1

您不应在更高范围内传递与类级变量同名的参数。局部变量将覆盖另一个，这意味着您的 setter 中的此语句:

dblRetailPrice = 1.1 * dblWholesalePrice

将设置您刚刚传入的 dblRetailPrice 临时参数的值，而不是您的类级 dblWholesalePrice 成员变量。

简单的解决方案是通过删除无用的类型符号前缀来更改参数的名称:

Public Class MyClass

    Protected dblRetailPrice As Double

    Public ReadOnly Property RetailPrice() As Double
        Get
           Return dblRetailPrice
        End Get
    End Property

    Public Overridable Sub UpdatePrice(ByVal retailPrice As Double)

       If dblWholesalePrice < 0 Then
           MessageBox.Show("Please input an amount greater than 0,wholesale price has not changed", "error")
       Else
           dblRetailPrice = 1.1 * dblWholesalePrice
       End If
    End Sub

End Class