Simple Fixed Array: Part 2

Introduction

In the last tutorial, we had a fixed array of elements (animals), and when we selected one of the radio buttons, a label would show us which number the element was. But, what if we had more than just six elements as in our array? Say, we had 500 elements and we needed to find out which element number the giraffe was? Well, that's where Array.IndexOf() comes in to play. So, in part two of this tutorial, we will use Array.IndexOf(). We will also place all the elements into a list box, and then we will use Array.Sort() to rearrange the elements in alphabetical order. So let's start with the Dim statements as follows:

Dim arrAnimal(6) As String
Dim AnimalIndex As Integer
Dim i As Integer

You will notice a change this time in the way we have dimensioned the array. Last time, we placed the elements like this: Dim arrAnimal() as String{"Lion","Tiger",Etc}, and this time, we have not placed the elements in the array, we have just set a number inside the parentheses to let the array know that we intend to place 6 elements inside it at a later stage in the program. The next piece of code is when the Form load. This is the point in this program when the elements are placed inside the array.

Private Sub AnimalArray_Load(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles MyBase.Load
    arrAnimal(0) = "Lion"
    arrAnimal(1) = "Tiger"
    arrAnimal(2) = "Giraffe"
    arrAnimal(3) = "Bear"
    arrAnimal(4) = "Elephant"
    arrAnimal(5) = "Monkey"
End Sub

Now, let's change the RadioButton1_CheckedChanged event so that when it is checked, lblDisplay.Text will show us which element number the animal is. You will also notice that we are using the concatenation character, &, to join different parts of the text together. We have also used Chr(13). This is the Enter button on the keyboard, and tells the program to place the text that comes after it on to a new line. In the case of RadioButton1, we want to know which element number Lion is: (Array.IndexOf(arrAnimal, "Lion").

Private Sub RadioButton1_CheckedChanged(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles RadioButton1.CheckedChange
    lblDisplay.Text = "The Lion" & Chr(13) & "is Element [" & 
       (Array.IndexOf(arrAnimal, "Lion")) & "]" & Chr(13) & "in the Array"
End Sub

We do the same for the other five RadioButtons in our program. The next piece of code places all of the elements in our array into a list box when we click Button1, using a For Next Loop; notice the numbers 0 to 5, this is because in an array, the first element index is 0.

Private Sub Button1_Click(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles btnShowall.Click
    For i = 0 To 5
        ListBox1.Items.Add(arrAnimal(i) & " is element [" & i & "] in the array")
    Next
End Sub

Now that the elements are in the ListBox, we can click on Button2 and get them sorted in alphabetical order using Array.Sort(). Notice that before we sort the elements, we clear the contents of the ListBox first using ListBox1.Items.Clear(). After sorting the array, if you click on one of the radio buttons, you will see that the element number now matches the sorted array, so that the Bear, element number [3] unsorted, is now element number [1].

Private Sub btnSort_Click(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles btnSort.Click
    ListBox1.Items.Clear()
    Array.Sort(arrAnimal)
    For i = 1 To 6
        ListBox1.Items.Add(arrAnimal(i) & " is element [" & i & "] in the array")
    Next
End Sub

Here is the complete code for you to copy (Ctrl C) and paste (Ctrl V).

Public Class AnimalArray
    Dim arrAnimal(6) As String
    Dim AnimalIndex As Integer
    Dim i As Integer

    Private Sub AnimalArray_Load(ByVal sender As System.Object, _
                   ByVal e As System.EventArgs) Handles MyBase.Load
        arrAnimal(0) = "Lion"
        arrAnimal(1) = "Tiger"
        arrAnimal(2) = "Giraffe"
        arrAnimal(3) = "Bear"
        arrAnimal(4) = "Elephant"
        arrAnimal(5) = "Monkey"
    End Sub

    Private Sub RadioButton1_CheckedChanged(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles RadioButton1.CheckedChanged
        LblDisplay.Text = "The Lion" & Chr(13) & "is Element [" & _
          (Array.IndexOf(arrAnimal, "Lion")) & "]" & Chr(13) & "in the Array"
    End Sub

    Private Sub RadioButton2_CheckedChanged(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles RadioButton2.CheckedChanged
        LblDisplay.Text = "The Tiger" & Chr(13) & "is Element [" & _
               (Array.IndexOf(arrAnimal, "Tiger")) & "]" & Chr(13) & "in the Array"
    End Sub

    Private Sub RadioButton3_CheckedChanged(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles RadioButton3.CheckedChanged
        LblDisplay.Text = "The Giraffe" & Chr(13) & "is Element [" & _
               (Array.IndexOf(arrAnimal, "Giraffe")) & "]" & Chr(13) & "in the Array"
    End Sub

    Private Sub RadioButton4_CheckedChanged(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles RadioButton4.CheckedChanged
        LblDisplay.Text = "The Bear" & Chr(13) & "is Element [" & _
                (Array.IndexOf(arrAnimal, "Bear")) & "]" & Chr(13) & "in the Array"
    End Sub

    Private Sub RadioButton5_CheckedChanged(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles RadioButton5.CheckedChanged
        LblDisplay.Text = "The Elephant" & Chr(13) & " is Element [" & _
          (Array.IndexOf(arrAnimal, "Elephant")) & "]" & Chr(13) & "in the Array"
    End Sub

    Private Sub RadioButton6_CheckedChanged(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles RadioButton6.CheckedChanged
        LblDisplay.Text = "The Monkey" & Chr(13) & " is Element [" & _
           (Array.IndexOf(arrAnimal, "Monkey")) & "]" & Chr(13) & "in the Array"
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles btnShowall.Click
        For i = 0 To 5
            ListBox1.Items.Add(arrAnimal(i) & " is element [" & i & "] in the array"
        Next
    End Sub

    Private Sub btnSort_Click(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles btnSort.Click
        ListBox1.Items.Clear()
        Array.Sort(arrAnimal)
        For i = 1 To 6
            ListBox1.Items.Add(arrAnimal(i) & " is element [" & i & "] in the array")
        Next
    End Sub
End Class