`ToString`

We can provide a custom ToString function on a VB.NET class. By using an Overrides ToString function, we specify how an instance renders itself as a String.

ToString() should use the Overrides modifier. This will cause it to be used as the implementation for less derived type references such as Object.

This program introduces the Perl class. This class, by default, inherits from the Object class. On the Object class (not shown) there exists an Overridable Function ToString.

Note The Perl class here provides the implementation that overrides ToString.

Info When Perl is used as an Object, its custom ToString implementation is still used.

Here When we construct the Perl instance, its fields are set to 2 and 3. It is passed to the Console.WriteLine subroutine as an Object.

Finally In Console.WriteLine, the ToString function is called on that Object. The Overrides Function ToString implementation is used.

Module Module1

    Class Perl

        Dim _a As Integer
        Dim _b As Integer

        Public Sub New(ByVal a As Integer, ByVal b As Integer)
            _a = a
            _b = b
        End Sub

        Public Overrides Function ToString() As String
            Return String.Format("[{0}, {1}]", _a, _b)
        End Function

    End Class

    Sub Main()
        Dim p As Perl = New Perl(2, 3)
        Console.WriteLine(p)
    End Sub

End Module
[2, 3]

A discussion

In the VB.NET language, we see Overridable functions and Overrides functions. These are equivalent to virtual and override methods in the C# language.

Detail The term "overridable" may be a clearer description of a virtual function. The term virtual is less obvious.

We looked at how you can provide the ToString function in your VB.NET program. This function returns a String. You can use any logic you wish to construct the String.