Object array

In VB.NET every variable or value derives from the Object type. Because of this, if we use an Object array, we can store multiple elements of any type.

With an Object array, a Function can accept any number of arguments—of any type. We gain a great degree of flexibility when the type system is used in this way.

Example

There are 2 subroutines in this program. The Main sub is the program's entry point. And in Write, we loop over an Object array and display each element with Console.WriteLine.

Imports System.Text

Module Module1

    Sub Main()
        ' Create an array of five elements.
        Dim arr(4) As Object
        arr(0) = New Object()
        arr(1) = New StringBuilder("Initialized")
        arr(2) = "Literal"
        arr(3) = 6
        arr(4) = Nothing
        ' Pass array to Subroutine.
        Write(arr)
    End Sub

    Sub Write(ByVal arr() As Object)
        ' Loop over each element.
        For Each element As Object In arr
            ' Avoid Nothing elements.
            If element IsNot Nothing Then
                Console.WriteLine(element)
                Console.WriteLine(element.GetType())
                Console.WriteLine("---")
            End If
        Next
    End Sub

End Module
System.Object
System.Object
---
Initialized
System.Text.StringBuilder
---
Literal
System.String
---
6
System.Int32
---

Testing against Nothing

The Object array can contain references with value Nothing. To avoid accessing these Nothing elements, we use the IsNot operator and compare against the Nothing literal.

The VB.NET language uses a powerful type hierarchy, which enables us to reference more derived types as their base type. We can store many different types inside an Object array.