Creating Arrays

A group of variables of the same data type is known as an array in Visual Basic 2015. If you only need to store a single value, one variable is enough. However, if you need to store many similar items, using separate variable names becomes tedious and hard to manage.

For example, if you want to store 100 customer names, it would be inconvenient to declare 100 different variables. Instead, you can declare one array and then refer to each item by its position:

Name(0), Name(1), Name(2), Name(3) ...

Each position number is called an index or subscript.

In Visual Basic 2015, an array can be one-dimensional or multidimensional. Most simple programs use one-dimensional or two-dimensional arrays.

A one-dimensional array is like a list of items arranged in one row or one column. A two-dimensional array is like a table made up of rows and columns.

To reference an element in a one-dimensional array, use:

ArrayName(x)

To reference an element in a two-dimensional array, use:

ArrayName(x, y)

In Visual Basic 2015, you can use either the Dim statement or the Public statement to declare an array.

• Dim creates an array that is local to a procedure or module.
• Public creates an array that can be used throughout the application.

The syntax for a one-dimensional array is:

Dim arrayName(n) As dataType

Here, n indicates the last index in the array, not the number of elements. Since Visual Basic arrays normally start at index 0, an array declared as (10) actually contains 11 elements, from index 0 through index 10.

Dim CusName(10) As String

The array above contains 11 string elements:

CusName(0) ... CusName(10)

To find the total number of elements in an array, use:

arrayName.Length

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    Dim CusName(10) As String
    MsgBox(CusName.Length)

End Sub

When the program runs, the message box displays the length of the array, which is 11.

You can also declare an array and initialize it with values in a more flexible way:

Dim arrayName As DataType()
arrayName = New String() {1, 2, 3, ...., n}

This approach creates the array with the values you provide immediately.

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    Dim CusName As String()
    CusName = New String() {1, 2, 3}
    MsgBox(CusName.Length)

End Sub

In this example, the length of the array is 3 because the array contains three elements.

The syntax for declaring a two-dimensional array is:

Dim ArrayName(m, n) As dataType

Here, m and n are the last indices in the two dimensions. The total number of elements is:

(m + 1) × (n + 1)

For example, if you declare:

Dim CusName(5, 6) As String

then the total number of elements is:

(5 + 1) × (6 + 1) = 42

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    Dim CusName(5,6) As String
    MsgBox(CusName.Length)

End Sub

When the program runs, the message box displays the length of the array as 42.

The following example shows how to collect six customer names from the user and store them in an array. Each name is entered through an InputBox and then added to a ListBox.

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Dim num As Integer
    Dim CusName(5) As String

    For num = 0 To 5
        CusName(num) = InputBox("Enter the customer name", "Enter Name")
        ListBox1.Items.Add(CusName(num))
    Next
End Sub

This example combines several ideas you have learned earlier:

• InputBox collects user input.
• CusName(num) stores each entered name in the array.
• For...Next repeats the input process six times.
• ListBox1.Items.Add(...) displays the names in the list box.