VB.Net使类的行为类似于基本类型，例如String或Integer

Question

我已经使class的行为像一个变体MathVariant，它将保存任何值，但将始终使用一个数字值(0或1)进行简单的算术。我还需要对乘法和除法做更多的测试，但除此之外，它似乎运行得很好。

我想让MathVariant表现得像一个基本类型，这样我就可以像普通变量一样使用它。所以现在当我想要得到这个值的时候我必须得到.Value的属性。

这是一个代码的例子，我希望能够编写使用

Dim SomeValue As MathVariant = "12.11"
Dim AnotherValue As MathVariant = "3"
Dim Result As MathVariant = SomeValue + AnotherValue 
Console.WriteLine(Result) 'prints MyNameSpace.MathVariant
Console.WriteLine(Result.Value) 'returns desired result (15.11)

我想只是能够使用类的实例直接获得其值。我一直在寻找很长一段时间，不确定是否可能或如何做到这一点。我不确定我是否必须摆脱Value属性，或者是否有保留名称或什么，我意识到我的类代码很长，所以如果有人可以解释必须做出的更改，并可能显示一个或两个将被更改的子示例。

Public Class MathVariant
    Private m_Value As String
    'public version
    Public Property Value() As Object
        Get
            Dim m_value1 As Double
            If Double.TryParse(m_Value, m_value1) Then
                Return m_value1
            End If
            Return m_Value
        End Get
        Set(value As Object)
            m_Value = value.ToString()
        End Set
    End Property
    Public Sub New(Value As String)
        m_Value = Value
    End Sub
    Public Shared Widening Operator CType(ByVal value As String) As MathVariant
            Return New MathVariant(value)
    End Operator
    Public Shared Widening Operator CType(ByVal value As Decimal) As MathVariant
        Return New MathVariant(value.ToString())
    End Operator
    Public Shared Widening Operator CType(ByVal value As Double) As MathVariant
        Return New MathVariant(value)
    End Operator
    Public Shared Widening Operator CType(ByVal value As Integer) As MathVariant
        Return New MathVariant(value.ToString())
    End Operator
    Public Shared Narrowing Operator CType(ByVal value As MathVariant) As Double
        Return value.ToDouble()
    End Operator
    Public Shared Narrowing Operator CType(ByVal value As MathVariant) As Integer
        Return Convert.ToInt32(value.ToDouble())
    End Operator
    Public Shared Narrowing Operator CType(ByVal value As MathVariant) As String
        Return value.Value.ToString()
    End Operator
    Public Function ToDouble() As Double
        Dim test As Double
        If Double.TryParse(Me.Value.ToString(), test) Then
            Return test
        End If
        Return 0
    End Function
    'addition
    Public Shared Operator +(value1 As MathVariant, value2 As MathVariant) As MathVariant
        If TypeOf value1.Value Is Double And TypeOf value2.Value Is Double Then
            Return value1.ToDouble() + value2.ToDouble()
        ElseIf TypeOf value1.Value Is Double Then
            Return value1.ToDouble() + 0.0
        ElseIf TypeOf value2.Value Is Double Then
            Return 0.0 + value2.ToDouble()
        End If
        Return 0
    End Operator
    Public Shared Operator +(value1 As MathVariant, value2 As Object) As MathVariant
        If TypeOf value1.Value Is Double And TypeOf value2 Is Double Then
            Return value1.ToDouble() + value2
        ElseIf TypeOf value2 Is Double Then
            Return 0.0 + value2
        End If
        Return 0.0
    End Operator
    Public Shared Operator +(value1 As MathVariant, value2 As Double) As MathVariant
        If TypeOf value1.Value Is Double Then
            Return value1.ToDouble() + value2
        End If
        Return 0.0 + value2
    End Operator
    Public Shared Operator +(value1 As MathVariant, value2 As Integer) As MathVariant
        If TypeOf value1.Value Is Double Then
            Return value1.ToDouble() + Convert.ToDouble(value2)
        End If
        Return 0.0 + Convert.ToDouble(value2)
    End Operator
    'subtraction
    Public Shared Operator -(value1 As MathVariant, value2 As MathVariant) As MathVariant
        If TypeOf value1.Value Is Double And TypeOf value2.Value Is Double Then
            Return value1.ToDouble() - value2.ToDouble()
        ElseIf TypeOf value1.Value Is Double Then
            Return value1.ToDouble() - 0.0
        ElseIf TypeOf value2.Value Is Double Then
            Return 0.0 - value2.ToDouble()
        End If
        Return 0
    End Operator
    Public Shared Operator -(value1 As MathVariant, value2 As Object) As MathVariant
        If TypeOf value1.Value Is Double And TypeOf value2 Is Double Then
            Return value1.ToDouble() - value2
        ElseIf TypeOf value2 Is Double Then
            Return 0.0 - value2
        End If
        Return 0.0
    End Operator
    Public Shared Operator -(value1 As MathVariant, value2 As Double) As MathVariant
        If TypeOf value1.Value Is Double Then
            Return value1.ToDouble() - value2
        End If
        Return 0.0 - value2
    End Operator
    Public Shared Operator -(value1 As MathVariant, value2 As Integer) As MathVariant
        If TypeOf value1.Value Is Double Then
            Return value1.ToDouble() - Convert.ToDouble(value2)
        End If
        Return 0.0 - Convert.ToDouble(value2)
    End Operator
    'division
    Public Shared Operator /(value1 As MathVariant, value2 As MathVariant) As MathVariant
        If TypeOf value1.Value Is Double And TypeOf value2.Value Is Double Then
            Return value1.ToDouble() / value2.ToDouble()
        ElseIf TypeOf value1.Value Is Double Then
            Return value1.ToDouble() / 1.0
        ElseIf TypeOf value2.Value Is Double Then
            Return 1.0 / value2.ToDouble()
        End If
        Return 0
    End Operator
    Public Shared Operator /(value1 As MathVariant, value2 As Object) As MathVariant
        If TypeOf value1.Value Is Double And TypeOf value2 Is Double Then
            Return value1.ToDouble() / value2
        ElseIf TypeOf value2 Is Double Then
            Return 1.0 / value2
        End If
        Return 0.0
    End Operator
    Public Shared Operator /(value1 As MathVariant, value2 As Double) As MathVariant
        If TypeOf value1.Value Is Double Then
            Return value1.ToDouble() + value2
        End If
        Return 0.0 + value2
    End Operator
    Public Shared Operator /(value1 As MathVariant, value2 As Integer) As MathVariant
        If TypeOf value1.Value Is Double Then
            Return value1.ToDouble() + Convert.ToDouble(value2)
        End If
        Return 0.0 + Convert.ToDouble(value2)
    End Operator
    'multiplication
    Public Shared Operator *(value1 As MathVariant, value2 As MathVariant) As MathVariant
        If TypeOf value1.Value Is Double And TypeOf value2.Value Is Double Then
            Return value1.ToDouble() * value2.ToDouble()
        ElseIf TypeOf value1.Value Is Double Then
            Return value1.ToDouble() * 1.0
        ElseIf TypeOf value2.Value Is Double Then
            Return 1.0 * value2.ToDouble()
        End If
        Return 1.0
    End Operator
    Public Shared Operator *(value1 As MathVariant, value2 As Object) As MathVariant
        If TypeOf value1.Value Is Double And TypeOf value2 Is Double Then
            Return value1.ToDouble() * value2
        ElseIf TypeOf value2 Is Double Then
            Return 1.0 * value2
        End If
        Return 1.0
    End Operator
    Public Shared Operator *(value1 As MathVariant, value2 As Double) As MathVariant
        If TypeOf value1.Value Is Double Then
            Return value1.ToDouble() + value2
        End If
        Return 1.0 * value2
    End Operator
    Public Shared Operator *(value1 As MathVariant, value2 As Integer) As MathVariant
        If TypeOf value1.Value Is Double Then
            Return value1.ToDouble() * Convert.ToDouble(value2)
        End If
        Return 1.0 * Convert.ToDouble(value2)
    End Operator

    'less than
    Public Shared Operator <(value1 As MathVariant, value2 As MathVariant)
        If TypeOf value1.Value Is Double And TypeOf value2.Value Is Double Then
            Return value1.Value < value2.Value
        ElseIf TypeOf value1.Value Is Double Then
            Return value1.Value < 0
        ElseIf TypeOf value2.Value Is Double Then
            Return 0 < value2.Value
        End If
        Return False
    End Operator
    Public Shared Operator <(value1 As MathVariant, value2 As Double)
        If TypeOf value1.Value Is Double Then
            Return value1.Value < value2
        Else
            Return 0 < value2
        End If
        Return False
    End Operator
    Public Shared Operator <(value1 As MathVariant, value2 As Integer)
        If TypeOf value1.Value Is Double Then
            Return value1.Value < Convert.ToDouble(value2)
        Else
            Return 0.0 < Convert.ToDouble(value2)
        End If
        Return False
    End Operator
    'greater than
    Public Shared Operator >(value1 As MathVariant, value2 As MathVariant)
        If TypeOf value1.Value Is Double And TypeOf value2.Value Is Double Then
            Return value1.Value > value2.Value
        ElseIf TypeOf value1.Value Is Double Then
            Return value1.Value > 0
        ElseIf TypeOf value2.Value Is Double Then
            Return 0 > value2.Value
        End If
        Return False
    End Operator
    Public Shared Operator >(value1 As MathVariant, value2 As Double)
        If TypeOf value1.Value Is Double Then
            Return value1.Value > value2
        Else
            Return 0 > value2
        End If
        Return False
    End Operator
    Public Shared Operator >(value1 As MathVariant, value2 As Integer)
        If TypeOf value1.Value Is Double Then
            Return value1.Value > Convert.ToDouble(value2)
        Else
            Return 0.0 > Convert.ToDouble(value2)
        End If
        Return False
    End Operator
    'equal to
    Public Shared Operator =(value1 As MathVariant, value2 As Object)
        If TypeOf (value2) Is Double Then
            Return Convert.ToDouble(value2).Equals(value1.ToDouble())
        ElseIf TypeOf (value2) Is String Then
            Return Convert.ToString(value2).Equals(value1.ToString())
        End If
        Return False
    End Operator
    'not equal
    Public Shared Operator <>(value1 As MathVariant, value2 As Object)
        Dim m_Type As Type = value2.GetType()
        If TypeOf (value2) Is Double Then
            Return Convert.ToDouble(value2).Equals(value1.ToDouble())
        ElseIf TypeOf (value2) Is String Then
            Return Convert.ToString(value2).Equals(value1.ToString())
        End If
        Return False
    End Operator
End Class

编辑:

这是我用上面的代码制作的。net fiddle的链接。

https://dotnetfiddle.net/bFlyhG

Answer 1

它似乎在大多数情况下工作，除了当你使用Console.WriteLine()。重写 ToString()方法似乎可以解决这个问题。

Public Overrides Function ToString() As String
    Return m_Value
End Function

也接受Andrew关于打开Option Strict的建议(至少暂时)。通过这样做，您可以看到代码中需要修复的地方，以便使其尽可能优化(转换方面)。