VB.Net/Data Structure/Array

Array IndexOf and LastIndexOf

Imports System
Public Class MainClass
    
    Shared Sub Main(ByVal args As String())
        Dim values(10) As Integer
        For i As Integer = 0 To 10
            values(i) = i
        Next i
        Console.WriteLine(Array.IndexOf(values, 6).ToString)
        Console.WriteLine(Array.LastIndexOf(values, 3).ToString)
    End Sub
End Class

Array Length Property

Imports System
Imports System.Diagnostics

Public Class MainClass
    Shared Sub Main()
        Dim arr(99) As Integer
        For i As Integer = 0 To 99
            arr(i) = i * i
        Next i
        Console.WriteLine(arr.Length)
    End Sub
End Class

Array Performance Test: One-dimensional array

Imports System
Imports System.Collections
Public Class MainClass
    
    Shared Sub Main(ByVal args As String())
        Dim start_time As DateTime
        Dim stop_time As DateTime
        Dim elapsed_time As TimeSpan
        " Get the number of items.
        Dim num_items As Integer = 10000
        " One-dimensional array.
        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().ToString )
    End Sub
End Class

Array Performance Test: SetValue(i, i)

Imports System
Imports System.Collections
Public Class MainClass
    
    Shared Sub Main(ByVal args As String())
        Dim start_time As DateTime
        Dim stop_time As DateTime
        Dim elapsed_time As TimeSpan
        " Get the number of items.
        Dim num_items As Integer = 1000000
        " One-dimensional Array.
        Dim array3 As Array = _
            Array.CreateInstance(GetType(Integer), num_items)
        start_time = Now
        For i As Integer = 0 To num_items - 1
            array3.SetValue(i, i)
        Next i
        stop_time = Now
        elapsed_time = stop_time.Subtract(start_time)
        Console.WriteLine( elapsed_time.TotalSeconds().ToString )

    End Sub
End Class

Array UBound

Public Class MainClass
   Public Shared Sub Main()
        Dim arrMyIntArray1(20) As Integer
        Dim arrMyIntArray2() As Integer = {1, 2, 3, 4}
        Dim arrMyIntArray3(4, 2) As Integer
        Dim arrMyIntArray4(,) As Integer = _
        {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}, {13, 14, 15, 16}}
        Dim arrMyIntArray5() As Integer
        Console.WriteLine(CStr(UBound(arrMyIntArray2)))
        arrMyIntArray2.GetUpperBound(0)
        Dim intLoop1 As Integer
        Dim intLoop2 As Integer
        For intLoop1 = 0 To UBound(arrMyIntArray4)
            For intLoop2 = 0 To UBound(arrMyIntArray4, 2)
                Console.WriteLine(arrMyIntArray4(intLoop1, intLoop2).ToString)
            Next
        Next
        
   End Sub
End Class

Array Upper Bound and Lower Bound

Imports System
Public Class MainClass
    Shared Sub Main(ByVal args As String())
        Dim friends() As String = {"1", "2", "3","4", "5"}
        Console.WriteLine("Upper bound: " & UBound(friends), "Array Demo")
        Console.WriteLine("Lower bound: " & LBound(friends), "Array Demo")
        Array.Sort(friends)
        Dim upperBound As Integer = friends.Length
        Dim random As New System.Random()
        Dim n As Integer
        For n = 1 To 10
            Dim index As Integer = random.Next(upperBound)
            Console.WriteLine(index & ": " & friends(index))
        Next
    End Sub
    
End Class

A simple class to store in the array

Imports System
Public Class MainClass
    
    Shared Sub Main()
         Dim intArray As Integer(  )
         Dim empArray As Employee(  )
         intArray = New Integer(5) {}
         empArray = New Employee(3) {}
         "populate the array
         Dim i As Integer
         "for indices 0 through 3
         For i = 0 To empArray.Length - 1
             empArray(i) = New Employee(i + 5)
             i = i + 1
         Next
    End Sub
End Class

 Public Class Employee
     Private empID As Integer
     "constructor
     Public Sub New(ByVal empID As Integer)
         Me.empID = empID
     End Sub
 End Class

Bounded array Example

Imports System
Imports System.Data
Imports System.Collections
public class MainClass
   Shared Sub Main()
        Dim X As Array
        Dim I As Integer
        Dim Lengths(0) As Integer
        Dim LowerBounds(0) As Integer
        Lengths(0) = 10
        LowerBounds(0) = 1
        X = Array.CreateInstance(GetType(System.Int32), Lengths, LowerBounds)
        Try
            X.SetValue(5, 0)
        Catch e As Exception
            Console.WriteLine(e.Message)
        End Try
        X.SetValue(6, 1)
        Console.WriteLine(X.GetValue(1))
   End Sub
End Class

Declare an Array and reference its member

Imports System
Public Class MainClass
    Shared Sub Main()
        "Declare an array
        Dim strFriends(4) As String
        "Populate the array
        strFriends(0) = "R"
        strFriends(1) = "B"
        strFriends(2) = "S"
        strFriends(3) = "S"
        strFriends(4) = "K"
        "Add the first array item to the list
        System.Console.WriteLine(strFriends(0))
    End Sub
End Class

Declaring, allocating and initializing arrays

Imports System
Public Class MainClass
    Shared Sub Main(ByVal args As String())
      Dim i As Integer
      Dim array As Integer()          " declare array variable
      Dim array1, array2 As Integer() " declare two arrays
      array = New Integer(9) {} " allocate memory for array
      " initializer list specifies number of elements
      " and value of each element
      array1 = New Integer() {32, 27, 64, 18, 95, _
         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 & "Array" & vbTab & _
         "Array1" & vbTab & "Array2" & vbCrLf )
      " display values in array
      For i = 0 To array.GetUpperBound(0)
         Console.WriteLine( i & vbTab & array(i) & vbTab & _
            array1(i) & vbTab & array2(i) & vbCrLf )
      Next
      Console.WriteLine(  vbCrLf & "The array contains " & _
         array.Length & " elements." )
    End Sub
End Class

For Each loops through Array

Imports System
Public Class MainClass
    
    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
End Class
 Public Class Employee
     Private empID As Integer
     "constructor
     Public Sub New(ByVal empID As Integer)
         Me.empID = empID
     End Sub
 End Class

Free array"s memory

Imports System
Imports System.Collections
Public Class MainClass
    
    Shared Sub Main(ByVal args As String())
        " Get the number of items.
        Dim num_items As Integer = 10000
        " One-dimensional array.
        Dim array1(0 To num_items - 1) As Integer
        For i As Integer = 0 To num_items - 1
            array1(i) = i
        Next i
        " Free the first array"s memory.
        Erase array1
    End Sub
End Class

Init an Array in Declaration

Imports System
Public Class MainClass
    Shared Sub Main(ByVal args As String())
        Dim friends() As String = {"1", "2", "3","4", "5"}

        Dim upperBound As Integer = friends.Length
        Dim random As New System.Random()
        Dim n As Integer
        For n = 1 To 10
            Dim index As Integer = random.Next(upperBound)
            Console.WriteLine(index & ": " & friends(index))
        Next
    End Sub
    
End Class

Reference an Element in an Array by Index

Imports System
Public Class MainClass
    Shared Sub Main(ByVal args As String())
        Dim friends(4) As String
        friends(0) = "1"
        friends(1) = "2"
        friends(2) = "3"
        friends(3) = "4"
        friends(4) = "5"
        Console.WriteLine(friends(2))
    End Sub
    
End Class

Set Array Element Value by Index

Imports System

Public Class MainClass
   Shared Sub Main()
        Dim anArray As Array
        Dim l(0) As Integer
        Dim lowerBounds(0) As Integer
        l(0) = 7
        lowerBounds(0) = 1995
        "creates an array of objects numbered 1995 - 2002
        anArray = Array.CreateInstance(GetType(System.Int32), l, lowerBounds)
        anArray.SetValue(200000, 1995)
        anArray.SetValue(1000000, 2001)
        Console.WriteLine("The entry in position 1995 is " & _
        (anArray.GetValue(1995).ToString))
        Console.WriteLine("The entry in position 2002 is " & _
        (anArray.GetValue(2001).ToString))
   End Sub 
End Class

Store your won Class in an Array

Imports System
Public Class MainClass
    Shared Sub Main(ByVal args As String())
         Dim intArray As Integer()
         Dim empArray As Employee()
         intArray = New Integer(5) {}
         empArray = New Employee(3) {}
         " populate the array
         Dim i As Integer
         " for indices 0 through 3
         For i = 0 To empArray.Length - 1
             empArray(i) = New Employee(i + 5)
             i = i + 1
         Next
    End Sub
End Class
 Public Class Employee
     Private empID As Integer
     " constructor
     Public Sub New(ByVal empID As Integer)
         Me.empID = empID
         Console.WriteLine(empID)
     End Sub
 End Class

Two ways to loop through Array

Imports System
Public Class MainClass
    
    Shared Sub Main()
     Dim intArray(  ) As Integer
     Dim empArray(  ) As Employee
     intArray = New Integer(5) {}
     empArray = New Employee(3) {}
     "populate the array
     Dim i As Integer
     For i = 0 To empArray.Length - 1
         empArray(i) = New Employee(i + 5)
     Next i
     Console.WriteLine("The Integer array...")
     Dim intValue As Integer
     For Each intValue In intArray
         Console.WriteLine(intValue.ToString(  ))
     Next
     Console.WriteLine("The Employee array...")
     Dim e As Employee
     For Each e In empArray
         Console.WriteLine(e)
     Next
    End Sub
End Class
 Public Class Employee
     Private empID As Integer
     "constructor
     Public Sub New(ByVal empID As Integer)
         Me.empID = empID
     End Sub
 End Class

Use Array CreateInstance to Create Array

Imports System
Public Class MainClass
    
    Shared Sub Main(ByVal args As String())
        Dim values As Array = _
            Array.CreateInstance(GetType(Integer), 11)
        For i As Integer = 0 To 10
            values.SetValue(i, i)
        Next i

        Console.WriteLine(Array.IndexOf(values, 6).ToString)
        Console.WriteLine(Array.LastIndexOf(values, 3).ToString)
    End Sub
End Class

Use For Each/Next to find a minimum grade

Imports System
Public Class MainClass
    Shared Sub Main(ByVal args As String())
      Dim gradeArray As Integer(,) = New Integer(,) {{1, 2, 3, 4}, {4, 3, 8, 1}, {7, 9, 8, 1}}
      Dim grade As Integer
      Dim lowGrade As Integer = 100
      For Each grade In gradeArray
         If grade < lowGrade Then
            lowGrade = grade
         End If
      Next
      Console.WriteLine("The minimum grade is: {0}", lowGrade)
    End Sub
End Class