How to format a Double by swapping a semicolon and keeping 2 decimal places in VB.NET

Question

I need to transform the result of a value of As Double for the Brazilian numerical standard that uses comma instead of dot (and also maintain only 2 decimal places), thus:

' variaveis de teste                       ' valores esperados de saida   
Dim t1 as double = 123                     ' ~> 123,00
Dim t2 as double = 123.123                 ' ~> 123,12
Dim t3 as double = 123123132112321321.123  ' ~> 123123132112321321,12
Dim t4 as double = 0.123                   ' ~> 0,12
Dim t4 as double = 0.158123                ' ~> 0,16

Answer 1

The method ToString has an overload that accepts a CultureInfo as parameter. Pass this parameter using the culture you want.

Dim valor = 5.89d
valor.ToString(new CultureInfo("pt-br"))

^{See working on . NET Fiddle}

Answer 2

A value Double is only a number, it has no formatting, it is only possible to turn it into String applying a formatting. This formatting should use a culture, in this case the Brazilian.

Imports System
Imports System.Globalization
                
Public Module Module1
    Public Sub Main()
        Dim ptbr = new CultureInfo("pt-br")
        Console.WriteLine("{0}", 123.ToString("N2", ptbr))
        Console.WriteLine("{0}", 123.123.ToString("N2", ptbr))
        Console.WriteLine("{0}", 123123132112321321.123d.ToString("N2", ptbr))
        Console.WriteLine("{0}", 0.123.ToString("N2", ptbr))
        Console.WriteLine("{0}", 0.158123.ToString("N2", ptbr))
    End Sub
End Module

Behold working in the ideone. And in the .NET Fiddle. Also put on the Github for future reference.

Just note that if this is money the Double is not the right kind.