`Join`

This VB.NET function combines many string elements into a single string. It acts on an array or List (we do not need to convert a List to an array first).

By using the Join function, we collapse these collections into String instances. This can help with file handing, or for storage of data in a database.

First example

This program creates an array of 3 strings. Then, we invoke the String.Join function on this array with the first argument being a string literal.

And The resulting string has the delimiter placed between all the elements—but not at the start or end.

Info Join requires a delimiter character and a collection of strings. It places this separator in between the strings in the result.

Module Module1
    Sub Main()
        ' Three-element array.
        Dim array(2) As String
        array(0) = "Dog"
        array(1) = "Cat"
        array(2) = "Python"

        ' Join array.
        Dim result As String = String.Join(",", array)

        ' Display result.
        Console.WriteLine(result)
    End Sub
End Module
Dog,Cat,Python

Example 2

You can specify the elements you want to join directly inside the String.Join call. Just pass more than 2 arguments to the String.Join function.

Tip Arguments after the first are joined together—the first is the delimiter.

Module Module1
    Sub Main()
        ' Join array.
        Dim result As String = String.Join("-", "Dot", "Net", "Perls")

        ' Display result.
        Console.WriteLine(result)
    End Sub
End Module
Dot-Net-Perls

Example 3

You can also join objects together into a single string. In the VB.NET language, each object can be converted into a String.

Info This String.Join function converts each object to a string and then joins those strings together.

Module Module1
    Sub Main()
        ' Join array.
        Dim result As String = String.Join("/", 1, 2, 3, "VB.NET")

        ' Display result.
        Console.WriteLine(result)
    End Sub
End Module
1/2/3/VB.NET

`Join` `List`

What should you do if you need to join the elements of a List? We can just pass the List directly to Join. This feature was added in newer versions of .NET.

Module Module1
    Sub Main()
        ' List.
        Dim list As List(Of String) = New List(Of String)
        list.Add("Dot")
        list.Add("Net")
        list.Add("Perls")

        ' Join list.
        Dim result As String = String.Join("*", list)

        ' Display result.
        Console.WriteLine(result)
    End Sub
End Module
Dot*Net*Perls

A summary

The String.Join function provides the opposite effect of the Split function. It takes a collection of elements and combines them into a single string separated by a delimiter.