MSDN Documentation

Arrays in VB.NET

Arrays are fundamental data structures in VB.NET that allow you to store a fixed-size sequence of elements of the same type. They are incredibly useful for managing collections of data efficiently.

Declaring and Initializing Arrays

You can declare an array by specifying its type and dimensions, followed by an empty set of parentheses (()). Initialization can be done using the New keyword and providing initial values.

One-Dimensional Arrays

A one-dimensional array is a sequence of elements accessed by a single index.

' Declare an array of integers
            Dim numbers(9) As Integer ' Creates an array with 10 elements (indices 0 to 9)

            ' Declare and initialize an array of strings
            Dim names() As String = {"Alice", "Bob", "Charlie"} ' Array size is determined by the number of elements provided
            

Multi-Dimensional Arrays

Arrays can have more than one dimension, allowing for more complex data structures like matrices.

' Declare a 2D array (matrix) of doubles
            Dim matrix(2, 3) As Double ' Creates a 3x4 matrix (indices 0 to 2 for the first dimension, 0 to 3 for the second)

            ' Declare and initialize a 3D array
            Dim cube(,,) As Integer = {{{1, 2}, {3, 4}}, {{5, 6}, {7, 8}}}
            

Accessing Array Elements

Elements in an array are accessed using their index enclosed in parentheses. Remember that array indices in VB.NET are zero-based.

Dim scores(4) As Integer
            scores(0) = 95
            scores(1) = 88
            scores(2) = 76
            scores(3) = 92
            scores(4) = 85

            Dim firstScore As Integer = scores(0)  ' firstScore will be 95
            Dim thirdScore As Integer = scores(2) ' thirdScore will be 76

            Dim myMatrix(1, 1) As String
            myMatrix(0, 1) = "Hello"
            Dim value As String = myMatrix(0, 1) ' value will be "Hello"
            

Array Properties and Methods

Arrays have useful properties and methods:

• Length: Returns the total number of elements in a one-dimensional array. For multi-dimensional arrays, use GetLength(dimension).
• Rank: Returns the number of dimensions in the array.
• Clear(): Sets all elements of an array to their default values (0 for numeric types, Nothing for object types).
• Sort(): Sorts the elements in a one-dimensional array.

Dim numbers() As Integer = {5, 2, 8, 1, 9}

            Console.WriteLine("Length of numbers array: " & numbers.Length) ' Output: 5
            Console.WriteLine("Rank of numbers array: " & numbers.Rank)   ' Output: 1

            Array.Sort(numbers) ' Sorts the array: {1, 2, 5, 8, 9}
            Console.WriteLine("First element after sorting: " & numbers(0)) ' Output: 1

            Array.Clear(numbers, 1, 3) ' Clears elements from index 1 to 3 (inclusive)
            ' numbers is now {1, 0, 0, 0, 9}
            

Jagged Arrays

Jagged arrays are arrays of arrays. Each inner array can have a different size.

' Declare a jagged array
            Dim jaggedArray(2)() As Integer ' An array that can hold 3 inner arrays

            ' Initialize the inner arrays with different sizes
            jaggedArray(0) = New Integer(3) {} ' First inner array has 4 elements
            jaggedArray(1) = New Integer(1) {} ' Second inner array has 2 elements
            jaggedArray(2) = New Integer(5) {} ' Third inner array has 6 elements

            ' Assign values
            jaggedArray(0)(2) = 10
            jaggedArray(1)(0) = 20
            jaggedArray(2)(4) = 30

            ' Accessing elements
            Console.WriteLine(jaggedArray(0)(2)) ' Output: 10
            Console.WriteLine(jaggedArray(1)(0)) ' Output: 20