Question

I have created a custom 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

But I can’t work out how I can test the value such as this:

    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

Error:

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

So how do I define Operators for my ValueType (I know this must be simple but I can’t find an exmaple anywhere!)?

Note I don’t want to test If v.Equals(x)

Answer 1

Something along the lines of the following (you’ll need to overload both the = and <> operators):

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

Note: You’ll probably want to implement IEquatable(Of MyValueType) as you’ll gain some benefits from doing this and would be considered a “best practice.”