Question

我创建了一个自定义ValueType：

Private Structure MyValueType
    Private _integerValue As Integer

    Public Sub New(initValue As Integer)
        _integerValue = initValue
    End Sub

    Public Overrides Function ToString() As String
        Return _integerValue.ToString
    End Function
End Structure

但我无法弄清楚如何测试这样的值：

    Dim v As New MyValueType(3)
    Dim x As New MyValueType(4)

    If v = x Then 'fails compile
        MessageBox.Show("The values are the same")
    End If

错误：

Operator '='  is not defined for Types MyValueType and MyValueType

那么如何为我的ValueType定义运算符（我知道这一定很简单，但我无法在任何地方找到它！）

注意我不想测试If v.Equals(x)

Answer 1

以下内容（您需要重载=和<>运算符）：

Sub Main
    Dim v As New MyValueType(3)
    Dim x As New MyValueType(4)

    If v <> x Then 'fails compile
        Console.WriteLine("The values are not the same")
    End If    
End Sub

Private Structure MyValueType
    Private _integerValue As Integer

    Public Sub New(initValue As Integer)
        _integerValue = initValue
    End Sub

    Public Overrides Function ToString() As String
        Return _integerValue.ToString
    End Function

    Public Shared Operator =(
        ByVal left as MyValueType, 
        ByVal right as MyValueType) As Boolean

        If left.ToString() = right.ToString()
            Return True
        End If

        Return False   
    End Operator 

    Public Shared Operator <>(
        ByVal left as MyValueType, 
        ByVal right as MyValueType) As Boolean          

        Return Not (left = right)   
    End Operator     
End Structure

注意：您可能希望实施IEquatable(Of MyValueType)，因为您可以从中获得一些好处，并被视为“最佳做法”。

无法设置自定义ValueType的“值”

1 个答案: