Interlocked.Increment Method (Int32)

Imports Microsoft.VisualBasic
Imports System
Imports System.Threading

Public Class Test

    <MTAThread> _
    Shared Sub Main()
        Dim thread1 As New Thread(AddressOf ThreadMethod)
        Dim thread2 As New Thread(AddressOf ThreadMethod)
        thread1.Start()
        thread2.Start()
        thread1.Join()
        thread2.Join()

        ' Have the garbage collector run the finalizer for each 
        ' instance of CountClass and wait for it to finish.
        GC.Collect()
        GC.WaitForPendingFinalizers()

        Console.WriteLine("UnsafeInstanceCount: {0}" & _
            vbCrLf & "SafeCountInstances: {1}", _
            CountClass.UnsafeInstanceCount.ToString(), _
            CountClass.SafeInstanceCount.ToString())
   End Sub 

   Shared Sub ThreadMethod()
        Dim cClass As CountClass 

        ' Create 100,000 instances of CountClass. 
        For i As Integer = 1 To 100000
            cClass = New CountClass()
        Next i
   End Sub 

End Class 

Public Class CountClass

    Shared unsafeCount As Integer = 0
    Shared   safeCount As Integer = 0

    Shared ReadOnly Property UnsafeInstanceCount As Integer 
        Get 
            Return unsafeCount
        End Get 
    End Property 

    Shared ReadOnly Property SafeInstanceCount As Integer 
        Get 
            Return safeCount
        End Get 
    End Property 

    Sub New()
        unsafeCount += 1
        Interlocked.Increment(safeCount)
    End Sub 

    Protected Overrides Sub Finalize()
        unsafeCount -= 1
        Interlocked.Decrement(safeCount)
        MyBase.Finalize()
    End Sub 

End Class