Overloading in VB.NET

VB.NET allows user-defined types to overload operators by defining static member functions using the operator keyword. The operator keyword is used to declare an operator in a class or struct declaration. Not all operators can be overloaded, and some that can be overloaded have certain restrictions, as listed in the given below Table.

The given below example illustrates overloading on complex numbers.

Example of Operator Overloading 

    Imports System
    Public Class Complex
        Public real As Integer = 0
        Public imaginary As Integer = 0

        Public Sub New(ByVal real As Integer, ByVal imaginary As Integer)
            Me.real = real
            Me.imaginary = imaginary
        End Sub
        Public Shared Operator +(ByVal c1 As Complex, ByVal c2 As Complex) As Complex
            Return New Complex(c1.real + c2.real, c1.imaginary + c2.imaginary)
        End Operator

        Public Shared Sub Main()
            Dim num1 As New Complex(2, 3)
            Dim num2 As New Complex(3, 4)
            Dim sum As Complex = num1 + num2
            Console.WriteLine("Real: {0}", sum.real)
            Console.WriteLine("Imaginary: {0}", sum.imaginary)
            Console.ReadLine()
        End Sub
    End Class

Screen Output Generated from the above code



The next example presents a more sophisticated example of operator overloading.

Example of Sophisticated Operator Overloading

    Imports System
    Class Rectangle
        Private iHeight As Integer
        Private iWidth As Integer

        Public Sub New()
            Height = 0
            Width = 0
        End Sub

        Public Sub New(ByVal w As Integer, ByVal h As Integer)
            Width = w
            Height = h
        End Sub

        Public Property Width() As Integer
            Get
                Return iWidth
            End Get
            Set(ByVal value As Integer)
                iWidth = value
            End Set
        End Property

        Public Property Height() As Integer
            Get
                Return iHeight
            End Get
            Set(ByVal value As Integer)
                iHeight = value
            End Set
        End Property

        Public ReadOnly Property Area() As Integer
            Get
                Return Height * Width
            End Get
        End Property
       
        Public Shared Operator =(ByVal a As Rectangle, ByVal b As Rectangle) As Boolean
            Return ((a.Height = b.Height) AndAlso (a.Width = b.Width))
        End Operator

        Public Shared Operator <>(ByVal a As Rectangle, ByVal b As Rectangle) As Boolean
            Return Not (a = b)
        End Operator

        Public Shared Operator >(ByVal a As Rectangle, ByVal b As Rectangle) As Boolean
            Return a.Area > b.Area
        End Operator

        Public Shared Operator <(ByVal a As Rectangle, ByVal b As Rectangle) As Boolean
            Return Not (a > b)
        End Operator

        Public Shared Operator >=(ByVal a As Rectangle, ByVal b As Rectangle) As Boolean
            Return (a > b) OrElse (a = b)
        End Operator

        Public Shared Operator <=(ByVal a As Rectangle, ByVal b As Rectangle) As Boolean
            Return (a < b) OrElse (a = b)
        End Operator

        Public Overrides Function Equals(ByVal o As Object) As Boolean
            Return Me.Equals(o)
        End Function

        Public Overrides Function GetHashCode() As Integer
            Return Me.GetHashCode()
        End Function

        Public Overrides Function ToString() As [String]
            Return "Height=" + Height + ",Width=" + Width
        End Function

        Public Shared Sub Main()
            Dim objRect1 As New Rectangle()
            Dim objRect2 As New Rectangle()
            Dim objRect3 As New Rectangle(10, 15)
            objRect1.Height = 15
            objRect1.Width = 10
            objRect2.Height = 25
            objRect2.Width = 10
            Console.WriteLine("Rectangle#1 ", objRect1)
            Console.WriteLine("Rectangle#2 ", objRect2)
            Console.WriteLine("Rectangle#3 ", objRect3)
            If objRect1 = objRect2 Then
                Console.WriteLine("Rectangle1 & Rectangle2 are Equal.")
            Else
            If objRect1 > objRect2 Then
                Console.WriteLine("Rectangle1 is greater than Rectangle2")
            Else
            Console.WriteLine("Rectangle1 is lesser than Rectangle2")
            End If
            End If
            If objRect1 = objRect3 Then
                Console.WriteLine("Rectangle1 & Rectangle3 are Equal.")
            Else
                Console.WriteLine("Rectangle1 & Rectangle3 are not Equal.")
            End If
            Console.ReadLine()
        End Sub
    End Class

Screen Output Generated from the above code



Conclusion

Hope this article would have helped you in understanding Overloading in VB.NET.