`Tuple`

In VB.NET a Tuple groups related pieces of data. With the useful Tuple type, we pass multiple values to a function or return multiple values.

This type is useful for grouping relating values into a small class. Using tuples tends to reduce program complexity—but they are not always ideal.

First example

We create a Tuple by using the VB.NET language's syntax for generic constructs. We must specify each type of the fields in the Tuple at construction time.

Important We must initialize the tuple's items to their final values. They cannot be changed later.

Here In this example, we read the 3 fields Item1, Item2, and Item3. We can only read these fields. We cannot set them.

Detail We specify the types Integer, String and Boolean for our tuple's 3 items.

Module Module1
    Sub Main()
        ' Create new tuple instance with three items.
        Dim tuple As Tuple(Of Integer, String, Boolean) = _
            New Tuple(Of Integer, String, Boolean)(1, "dog", False)
        ' Test tuple properties.
        If (tuple.Item1 = 1) Then
            Console.WriteLine(tuple.Item1)
        End If

        If (tuple.Item2 = "rodent") Then
            Console.WriteLine(0)
        End If

        If (tuple.Item3 = False) Then
            Console.WriteLine(tuple.Item3)
        End If
    End Sub
End Module1
False

Example 2

How can you use the Tuple type with functions and subroutines in the VB.NET language? We first instantiate the Tuple as we did above.

And Returning a Tuple value can be declared in much the same way, and is not shown here.

Also This example demonstrates the use of another type (a reference type, StringBuilder) in a Tuple.

Imports System.Text

Module Module1
    Sub Main()
        ' Use this object in the tuple.
        Dim builder As StringBuilder = New StringBuilder()
        builder.Append("cat")

        ' Create new tuple instance with 3 items.
        Dim tuple As Tuple(Of String, StringBuilder, Integer) = _
            New Tuple(Of String, StringBuilder, Integer)("carrot", builder, 3)

        ' Pass tuple as parameter.
        F(tuple)
    End Sub

    Sub F(ByRef tuple As Tuple(Of String, StringBuilder, Integer))
        ' Evaluate the tuple.
        Console.WriteLine(tuple.Item1)
        Console.WriteLine(tuple.Item2)
        Console.WriteLine(tuple.Item3)
    End Sub
End Modulecarrot
cat
3

Return multiple values

A tuple can be used to return 2 or more values from a Function. We just declare the return type of the Function to be the required Tuple.

And Then we must return a tuple on each exit point of the Function. We access the return values with properties like Item1 and Item2.

Module Module1

    Function GetTwoValues() As Tuple(Of Integer, Integer)
        ' Return 2 values from this Function.
        Return New Tuple(Of Integer, Integer)(20, 30)
    End Function

    Sub Main()
        Dim result As Tuple(Of Integer, Integer) = GetTwoValues()
        Console.WriteLine("RETURN VALUE 1: {0}", result.Item1)
        Console.WriteLine("RETURN VALUE 2: {0}", result.Item2)
    End Sub

End ModuleRETURN VALUE 1: 20
RETURN VALUE 2: 30

Notes, tuples

A VB.NET class is self-documenting. Field names, and the type name, help us remember our intentions. But a tuple, which lacks those names, may be harder to understand.

A summary

The Tuple type is a clearly useful one in the VB.NET language. It provides a mechanism to create a class with several items in it without a separate type definition.