Loop, `String` array

Suppose you have a String array in your VB.NET program, and want to loop over its elements. This can be done in various ways in this language.

A For Each loop is the clearest and least error-prone, but other loops like For may be more useful in some programs. A For Step loop can be used to loop in reverse.

Example

To begin, we need to have a String array for our various loops. We use array initializer syntax to create a String array of 4 elements.

Step 1 We use the For Each loop over the "array1" elements. We use string interpolation syntax to print each element to the console.

Step 2 We loop over the indexes of the array with a For-loop. We go to the Length minus 1, so avoid reading past the end.

Step 3 We can also use For To loops to iterate backwards—we must specify a Step of -1.

Step 4 Here is a functional version of For Each—we call a Sub on each element in the array with Array.ForEach.

Module Module1
    Sub Main(args as String())
        Dim array1() As String = {"one", "two", "three", "four"}

        ' Step 1: loop over the array with For Each.
        For Each value in array1
            Console.WriteLine($"FOR EACH: {value}")
        Next

        ' Step 2: loop over the array with For.
        For i = 0 To array1.Length - 1
            Dim value as String = array1(i)
            Console.WriteLine($"FOR: {value}")
        Next

        ' Step 3: loop over the string array backwards.
        For i = array1.Length - 1 To 0 Step -1
            Dim value = array1(i)
            Console.WriteLine($"BACKWARDS: {value}")
        Next

        ' Step 4: loop with Array.ForEach subroutine with a lambda.
        Array.ForEach(array1, Sub(value As String)
            Console.WriteLine($"ForEach: {value}")
        End Sub)
    End Sub
End ModuleFOR EACH: one
FOR EACH: two
FOR EACH: three
FOR EACH: four
FOR: one
FOR: two
FOR: three
FOR: four
BACKWARDS: four
BACKWARDS: three
BACKWARDS: two
BACKWARDS: one
ForEach: one
ForEach: two
ForEach: three
ForEach: four

String arrays, like other arrays in VB.NET, can be looped over in several ways. We can use For loops, or even the Array.ForEach subroutine to call a subroutine repeatedly.

Loop, String array

Example

Loop, `String` array