VB.Net Tutorial/Collections/Array

Array Clone

Public Class Tester
    Public Shared Sub Main
        Dim arrayA() As String = {"One", "Two", "Three", "Four", "Five", "Six"}
        Console.WriteLine(Join(arrayA, ","))
        Dim arrayB() As String = {"A", "B", "C", "D", "E", "E", "F", "G", "H"}
        Console.WriteLine(Join(arrayB, ","))
        " ----- Make a reference copy.
        Dim arrayC() As String = arrayA
        Console.WriteLine(Join(arrayC, ","))
        " ----- Make a full, unique copy of all elements.
        Dim arrayD() As String = arrayA.Clone
        Console.WriteLine(Join(arrayD, ","))
    End Sub
End Class

One,Two,Three,Four,Five,Six
A,B,C,D,E,E,F,G,H
One,Two,Three,Four,Five,Six
One,Two,Three,Four,Five,Six

Array declaration

Option Strict On
Public Module Arrays
   Public Sub Main
      Dim arr As Array
      Dim int() As Integer = {12, 16, 20, 24, 28, 32}
      arr = CType(int, Array)
      Dim byFours() As Integer = {12, 24, 36, 48}
      Dim names() As String = {"K", "S", "S", "D", "N"}
      Dim miscData() As Object = {"this", 12d, 16ui, "a"c}
      Dim objArray() As Object
      miscData = names
      
      Dim myArray1a() As Integer " Uninitialized array
      Dim myArray1b As Integer() " Uninitialized array
      Dim myArray2(10) As Integer " 1-dimensional array with 11 elements
      Dim Employees1( , ) As Object " Uninitialized 2-D array
      Dim Employees(200, 2) As Object " 2-D array with 201 and 3 elements
      Dim jagged1(9)() As String
      Dim jagged2()() As String = New String(9)() {}
      Dim myArray1arr As Array
      Dim myArray2a As Array = Array.CreateInstance(GetType(Integer), 10)
      Dim members() As Integer = {3, 10}
      Dim myArray3a As Array = Array.CreateInstance(GetType(Integer), members)
   End Sub
End Module

Array length: negative

Option Strict On
Public Module ValidArray
   Public Sub Main()
      Dim emptyArray(-1) As String
      For Each element As String In emptyArray
         Console.WriteLine(element)
      Next
   End Sub
End Module

Array Resize

Public Class Tester
    Public Shared Sub Main
        Dim result As New System.Text.StringBuilder
        Dim arrayInsert() As String = {"O", "A", "G", "B", "B"}
        " ----- Show the contents before insertion.
        result.AppendLine("Before insertion:")
        For Each fruit As String In arrayInsert
            result.AppendLine(fruit)
        Next fruit
        " ----- Insert more fruit.
        InsertArrayElement(Of String)(arrayInsert, 2, "Lemons")
        " ----- Show the contents after insertion.
        result.AppendLine()
        result.AppendLine("After insertion:")
        For Each fruit As String In arrayInsert
            result.AppendLine(fruit)
        Next fruit
        Console.WriteLine(result.ToString())
    End Sub
    Public Shared Sub InsertArrayElement(Of T)( _
          ByRef sourceArray() As T, _
          ByVal insertIndex As Integer, _
          ByVal newValue As T)
        Dim newPosition As Integer
        Dim counter As Integer
        newPosition = insertIndex
        If (newPosition < 0) Then newPosition = 0
        If (newPosition > sourceArray.Length) Then _
           newPosition = sourceArray.Length
        Array.Resize(sourceArray, sourceArray.Length + 1)
        For counter = sourceArray.Length - 2 To newPosition Step -1
            sourceArray(counter + 1) = sourceArray(counter)
        Next counter
        sourceArray(newPosition) = newValue
    End Sub
End Class

Before insertion:
O
A
G
B
B
After insertion:
O
A
Lemons
G
B
B

Assing array element value by using index

public class Test
   public Shared Sub Main
        Dim arySalaries(15) As Integer
        Dim aryNames(15) As String
        Dim intCounter As Integer
        aryNames(0) = "J"
        arySalaries(0) = 34000
        aryNames(1) = "B"
        arySalaries(1) = 62000
        "Set other array elements here.
        aryNames(15) = "P"
        arySalaries(15) = 10300
        "Show the elements of the array.
        For intCounter = 0 To 15
            Console.WriteLine("Array element: " & intCounter & vbCrLf & _
                   "Name: " & aryNames(intCounter) & vbCrLf & _
                   "Salary: " & arySalaries(intCounter))
        Next intCounter

   End Sub

End class

Array element: 0
Name: J
Salary: 34000
Array element: 1
Name: B
Salary: 62000
Array element: 2
Name:
Salary: 0
Array element: 3
Name:
Salary: 0
Array element: 4
Name:
Salary: 0
Array element: 5
Name:
Salary: 0
Array element: 6
Name:
Salary: 0
Array element: 7
Name:
Salary: 0
Array element: 8
Name:
Salary: 0
Array element: 9
Name:
Salary: 0
Array element: 10
Name:
Salary: 0
Array element: 11
Name:
Salary: 0
Array element: 12
Name:
Salary: 0
Array element: 13
Name:
Salary: 0
Array element: 14
Name:
Salary: 0
Array element: 15
Name: P
Salary: 10300

Computing sum of elements in array.

Module Tester
   Sub Main()
      Dim array As Integer() = New Integer() _
         {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
      Dim total As Integer = 0, i As Integer = 0
      For i = 0 To array.GetUpperBound(0)
         total += array(i)
      Next
      Console.WriteLine("Total of array elements: " & total)
   End Sub 
End Module

Total of array elements: 55

Declaring and allocating an array

Module Tester
   Sub Main()
      Dim i As Integer
      Dim array As Integer()    " declare array variable
      array = New Integer(9) {} " allocate memory for array
      Console.WriteLine("Subscript " & vbTab & "Value")
      For i = 0 To array.GetUpperBound(0)
         Console.WriteLine( i & vbTab & array(i))
      Next
      Console.WriteLine("The array contains " & _
         array.Length & " elements.")
   End Sub 
   
End Module

Subscript       Value
0       0
1       0
2       0
3       0
4       0
5       0
6       0
7       0
8       0
9       0
The array contains 10 elements.

Display the contents of a single-dimension array

Public Class Tester
    Public Shared Sub Main
        Dim sourceArray() As Integer = {1, 2, 3}
        Dim result As New System.Text.StringBuilder
        Dim counter As Integer
        result.Append("{")
        For counter = 0 To sourceArray.Length - 1
            result.Append(sourceArray(counter).ToString())
            If (counter < (sourceArray.Length - 1)) Then result.Append(",")
        Next counter
        result.Append("}")
        Console.WriteLine(result.ToString())
        
    End Sub
End Class

{1,2,3}

Initialize Array element during declaration

Option Strict On
 Imports System
 Public Class Employee
     Private empID As Integer
     Public Sub New(ByVal empID As Integer)
         Me.empID = empID
     End Sub 
     Public Overrides Function ToString( ) As String
         Return empID.ToString( )
     End Function 
 End Class 
 
 Class Tester
 
     Public Shared Sub Main( )
         Dim intArray As Integer( ) = {2, 4, 6, 8, 10}
         Dim empArray As Employee( ) = _
           {New Employee(5), New Employee(7), New Employee(9)}
    
         Console.WriteLine("The Integer array...")
         Dim theInt As Integer
         For Each theInt In intArray
             Console.WriteLine(theInt.ToString( ))
         Next theInt
    
         Console.WriteLine("The employee array...")
         Dim e As Employee
         For Each e In empArray
             Console.WriteLine(e.ToString( ))
         Next e
     End Sub "Run
 End Class

The Integer array...
2
4
6
8
10
The employee array...
5
7
9

Initializing arrays

Module Tester
   Sub Main()
      Dim i As Integer
      Dim array1, array2 As Integer() " declare two arrays
      " initializer list specifies number of elements
      " and value of each element
      array1 = New Integer() {2, 7, 4, 8, 5, 14, 90, 70, 60, 37}
      " allocate array2 based on length of array1
      array2 = New Integer(array1.GetUpperBound(0)) {}
      " set values in array2 by a calculation
      For i = 0 To array2.GetUpperBound(0)
         array2(i) = 2 + 2 * i
      Next
      Console.WriteLine("Subscript " & vbTab & "Array1" & vbTab & _
         "Array2")
      " display values for both arrays
      For i = 0 To array1.GetUpperBound(0)
         Console.WriteLine(i & vbTab & array1(i) & vbTab & array2(i))
      Next
   End Sub 
End Module

Subscript       Array1  Array2
0       2       2
1       7       4
2       4       6
3       8       8
4       5       10
5       14      12
6       90      14
7       70      16
8       60      18
9       37      20

Insert element in the middle of an Array

Public Class Tester
    Public Shared Sub Main
        Dim result As New System.Text.StringBuilder
        Dim arrayInsert() As String = {"O", "A", "G", "B", "B"}
        " ----- Show the contents before insertion.
        result.AppendLine("Before insertion:")
        For Each fruit As String In arrayInsert
            result.AppendLine(fruit)
        Next fruit
        " ----- Insert more fruit.
        InsertArrayElement(Of String)(arrayInsert, 2, "Lemons")
        " ----- Show the contents after insertion.
        result.AppendLine()
        result.AppendLine("After insertion:")
        For Each fruit As String In arrayInsert
            result.AppendLine(fruit)
        Next fruit
        Console.WriteLine(result.ToString())
    End Sub
    Public Shared Sub InsertArrayElement(Of T)( _
          ByRef sourceArray() As T, _
          ByVal insertIndex As Integer, _
          ByVal newValue As T)
        Dim newPosition As Integer
        Dim counter As Integer
        newPosition = insertIndex
        If (newPosition < 0) Then newPosition = 0
        If (newPosition > sourceArray.Length) Then _
           newPosition = sourceArray.Length
        Array.Resize(sourceArray, sourceArray.Length + 1)
        For counter = sourceArray.Length - 2 To newPosition Step -1
            sourceArray(counter + 1) = sourceArray(counter)
        Next counter
        sourceArray(newPosition) = newValue
    End Sub
End Class

Before insertion:
O
A
G
B
B
After insertion:
O
A
Lemons
G
B
B

One dimesional array performance

public class Test
  
   public Shared Sub Main
        Dim start_time As DateTime
        Dim stop_time As DateTime
        Dim elapsed_time As TimeSpan
        Dim num_items As Integer = 10000
        Dim array1(0 To num_items - 1) As Integer
        start_time = Now
        For i As Integer = 0 To num_items - 1
            array1(i) = i
        Next i
        stop_time = Now
        elapsed_time = stop_time.Subtract(start_time)
        Console.WriteLine(elapsed_time.TotalSeconds())

        Erase array1
   End Sub
   
End class

0

Reorder the elements of an array in a random order

Public Class Tester
    Public Shared Sub Main
        Dim arrayShuffle() As String = {"A", "B", "C", "D", "E"}
        For Each fruit As String In arrayShuffle
            Console.WriteLine(fruit)
        Next fruit
        Shuffle(arrayShuffle)
        For Each fruit As String In arrayShuffle
            Console.WriteLine(fruit)
        Next fruit
    End Sub
    Public Shared Sub Shuffle(ByRef shuffleArray() As Object)
        Dim counter As Integer
        Dim newPosition As Integer
        Dim shuffleMethod As New Random
        Dim tempObject As Object
        For counter = 0 To shuffleArray.Length - 1
            newPosition = shuffleMethod.Next(0, shuffleArray.Length - 1)
            tempObject = shuffleArray(counter)
            shuffleArray(counter) = shuffleArray(newPosition)
            shuffleArray(newPosition) = tempObject
        Next counter
    End Sub
End Class

A
B
C
D
E
B
A
E
C
D

Swap elements in an array

Public Class Tester
    Public Shared Sub Main
        Dim result As New System.Text.StringBuilder
        Dim arraySwap() As String = {"A", "B", "C", "D", "E"}
        Swap(arraySwap, 1, 3)
        For Each fruit As String In arraySwap
            Console.WriteLine(fruit)
        Next fruit

    End Sub
    Public Shared Sub Swap(ByRef swapArray() As Object, _
            ByVal first As Integer, ByVal second As Integer)
        Dim tempObject As Object
        tempObject = swapArray(first)
        swapArray(first) = swapArray(second)
        swapArray(second) = tempObject
    End Sub
End Class

A
D
C
B
E

Two dimesional array performance

public class Test
  
   public Shared Sub Main
        Dim start_time As DateTime
        Dim stop_time As DateTime
        Dim elapsed_time As TimeSpan
        Dim num_items As Integer = 10000
        " Two-dimensional array.
        Dim array2(0 To 0, 0 To num_items - 1) As Integer
        start_time = Now
        For i As Integer = 0 To num_items - 1
            array2(0, i) = i
        Next i
        stop_time = Now
        elapsed_time = stop_time.Subtract(start_time)
        Console.WriteLine(elapsed_time.TotalSeconds())

        Erase array2
   End Sub
   
End class

0

Use For loop to initialize Integer array

Module Module1
    Sub Main()
        Dim Students(50) As Integer
        Dim I As Integer
        For I = 0 To 50
            Students(I) = I
        Next
        For I = 0 To 50
            Console.WriteLine(Students(I))
        Next
    End Sub
End Module

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