Visual Basic .NET Language Multithreading using Thread Class


This example uses the Thread Class, but multithreaded applications can also be made using BackgroundWorker. The AddNumber, SubstractNumber, and DivideNumber functions will be executed by separate threads:

Edit: Now the UI thread waits for the child threads to finish and shows the result.

Module Module1
    'Declare the Thread and assign a sub to that
    Dim AddThread As New Threading.Thread(AddressOf AddNumber)
    Dim SubstractThread As New Threading.Thread(AddressOf SubstractNumber)
    Dim DivideThread As New Threading.Thread(AddressOf DivideNumber)

    'Declare the variable for holding the result 
    Dim addResult As Integer
    Dim SubStractResult As Integer
    Dim DivisionResult As Double

    Dim bFinishAddition As Boolean = False
    Dim bFinishSubstration As Boolean = False
    Dim bFinishDivision As Boolean = False

    Dim bShownAdditionResult As Boolean = False
    Dim bShownDivisionResult As Boolean = False
    Dim bShownSubstractionResult As Boolean = False

    Sub Main()

        'Now start the trheads

        'Wait and display the results in console
        Console.WriteLine("Waiting for threads to finish...")

        While bFinishAddition = False Or bFinishDivision = False Or bFinishSubstration = False
            Threading.Thread.Sleep(50)     'UI thread is sleeping
            If bFinishAddition And Not bShownAdditionResult Then
                Console.WriteLine("Addition Result : " & addResult)
                bShownAdditionResult = True
            End If

            If bFinishSubstration And Not bShownSubstractionResult Then
                Console.WriteLine("Substraction Result : " & SubStractResult)
                bShownSubstractionResult = True
            End If

            If bFinishDivision  And Not bShownDivisionResult Then
                Console.WriteLine("Division Result : " & DivisionResult)
                bShownDivisionResult = True
            End If

        End While

        Console.WriteLine("Finished all threads.")
    End Sub

    Private Sub AddNumber()
        Dim n1 As Integer = 22
        Dim n2 As Integer = 11

        For i As Integer = 0 To 100
            addResult = addResult + (n1 + n2)
            Threading.Thread.Sleep(50)      'sleeping Add thread
        bFinishAddition = True
    End Sub

    Private Sub SubstractNumber()
        Dim n1 As Integer = 22
        Dim n2 As Integer = 11

        For i As Integer = 0 To 80
            SubStractResult = SubStractResult - (n1 - n2)
        bFinishSubstration = True
    End Sub

    Private Sub DivideNumber()
        Dim n1 As Integer = 22
        Dim n2 As Integer = 11
        For i As Integer = 0 To 60
            DivisionResult = DivisionResult + (n1 / n2)
        bFinishDivision = True
    End Sub

End Module