VB.NET - Multiple Return Values

Multiple return values. A function in VB.NET can only return one value—this can be a value type or a reference type (like a Class). But one value is not always sufficient.

Function

With ByRef arguments, we can set multiple output values. And with a structure like KeyValuePair (or a class like Tuple) we can return multiple values as one.

ByVal, ByRef

Example. This program has several versions of a GetTwoNumbers function. These all return 2 Integers, either by using ByRef arguments or a container to store the result.

DateTime

Part 1 The first version uses ByRef. It sets the two output parameters before it exits. We can use them in the calling location.

Part 2 The second version uses KeyValuePair. It returns a KeyValuePair created by calling the New KeyValuePair constructor.

KeyValuePair

Part 3 We use the Tuple class to return multiple values. A tuple can return many more than two values, but we just show two here.

Tuple

Part 4 We call the different versions of the GetTwoNumbers functions and print their output to verify their correctness.

Module Module1 Sub GetTwoNumbersA(ByRef number1 As Integer, ByRef number2 As Integer) ' Part 1: use ByRef parameters. number1 = 2 number2 = 3 End Sub Function GetTwoNumbersB() As KeyValuePair(Of Integer, Integer) ' Part 2: return a KeyValuePair. Return New KeyValuePair(Of Integer, Integer)(2, 3) End Function Function GetTwoNumbersC() As Tuple(Of Integer, Integer) ' Part 3: return a tuple. Return New Tuple(Of Integer, Integer)(2, 3) End Function Sub Main() ' Part 4: test the functions. Dim number1 As Integer Dim number2 As Integer GetTwoNumbersA(number1, number2) Console.WriteLine($"{number1} {number2}") Dim result2 = GetTwoNumbersB() Console.WriteLine($"{result2.Key} {result2.Value}") Dim result3 = GetTwoNumbersC() Console.WriteLine($"{result3.Item1} {result3.Item2}") End Sub End Module

2 3 2 3 2 3

Some notes. Often ByRef arguments are easier to use. This probably depends on how a programmer is thinking. But introducing Tuples or Pairs seems excessively complex to me.

And The concept of reference, output parameters is well-known in the programming world.

So Using a ByRef argument to return a value will yield code that is easily understood by others.

Summary. With ByRef, KeyValuePair and Tuple, we return many values from VB.NET Subs and Functions. This approach is powerful. Not all methods logically return just 1 value.

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This page was last updated on Oct 3, 2024 (new example).

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