[RESOLVED] Disposing Multiple Instantiated Objects (Classes) With Long Run-times

[pel11]

At run-time, my Winform app starts (instantiates) multiple classes which are all IDisposable. Each class spawns a threaded method which often has long run times (several minutes).

If a run only requires use of one class, then naturally I won't thread the method in that class and therefore can dispose the class immediately thereafter. The choice of threading the method or not is set by use of a boolean, for example, called threadAllMethods.

threadAllMethods = false
Dim MyMath1 as New MathClass1(param1, param2, param3)
MyMath1.Dispose()

If a run requires use of all classes, then I will thread the method in each class, so that use of multiple threads can run simultaneously.

threadAllMethods = true
Dim MyMath1 as New MathClass1(param1, param2, param3)
Dim MyMath2 as New MathClass2(param1, param2, param3)
Dim MyMath3 as New MathClass3(param1, param2, param3)
Dim MyMath4 as New MathClass4(param1, param2, param3)
Dim MyMath5 as New MathClass5(param1, param2, param3)

However, when all classes are instantiated and their methods are threaded, you cannot invoke Dispose immediately thereafter since you need to wait until the threads are completed. Therefore, I define a public list of Object type as follows:

Public ListOfClasses As New List(Of Object)

Next, after each class is instantiated with method threading, I add the object to the public list of objects:

threadAllMethods = true
Dim MyMath1 as New MathClass1(param1, param2, param3)
ListOfClasses.Add(MyMath1)
Dim MyMath2 as New MathClass2(param1, param2, param3)
ListOfClasses.Add(MyMath2)
Dim MyMath3 as New MathClass3(param1, param2, param3)
ListOfClasses.Add(MyMath3)
Dim MyMath4 as New MathClass4(param1, param2, param3)
ListOfClasses.Add(MyMath4)
Dim MyMath5 as New MathClass5(param1, param2, param3)
ListOfClasses.Add(MyMath5)

Then, by using AutoResetEvents with e.g. MyMath1ThreadDone.Set specified at the end of a threaded method, I wait for all threads (methods) to complete, and then dispose the IDisposable classes using the a Do While:

MyMath1ThreadDone.WaitOne()
MyMath2ThreadDone.WaitOne()
MyMath3ThreadDone.WaitOne()
MyMath4ThreadDone.WaitOne()
MyMath5ThreadDone.WaitOne()

While (ListOfClasses.Count() > 0)
   Dim item As Object = ListOfClasses(0)
   ListOfClasses.RemoveAt(0)
   item.Dispose
End While

FYI, the Dispose code I am using was fetched from MSDN a while ago, and I am not sure that it guarantees proper finalization:

#Region "IDisposable"
    '---Code entirely copied from MSDN
    Private managedResource As System.ComponentModel.Component
    Private unmanagedResource As IntPtr
    Protected disposed As Boolean = False

    Protected Overridable Overloads Sub Dispose(ByVal disposing As Boolean)
        If Not Me.disposed Then
            If disposing Then
                Try
                    ' managedResource.Dispose()
                Catch
                End Try
            End If
            ' Add code here to release the unmanaged resource.
            unmanagedResource = IntPtr.Zero
            ' Note that this is not thread safe. 
        End If
        Me.disposed = True
    End Sub

    'Do not change or add Overridable to these methods. 
    'Put cleanup code in Dispose(ByVal disposing As Boolean). 
    Public Overloads Sub Dispose() Implements IDisposable.Dispose
        Dispose(True)
        GC.SuppressFinalize(Me)
    End Sub
    Protected Overrides Sub Finalize()
        Dispose(False)
        MyBase.Finalize()
    End Sub
#End Region

Some questions I have are (a) When the methods inside all classes are to be threaded, is it appropriate to load the classes as objects into a list and then wait for all threads to stop and then dispose the classes, and (b) based on the MSDN dispose code I am using, will it finalize correctly, and will it release unmanaged resources as well? (As far as manually disposing GDIObjects, I just spent a lot of time making sure all the Pen, Brush, and bitmaps are individually disposed within their respective methods -- since GDIObjects tend to fill up Byte[] arrays that are unmanaged without handles and are not disposed via IDisposable).

Last, instead of loading all the classes into an object list, and then waiting for all their threaded methods to complete and then disposing classes en-block, can I use the following code at the end of a threaded method to invoke disposal of its parent class, as follows?

Sub DoTheMath(ByVal param1 As Double, ByVal param2 As Double, ByVal param3 As Double)

   '....do some work

    MyMath1ThreadDone.Set() 'always used/needed for thread mgmt
    Me.Dispose
End Sub