Need help reducing the Commit size of my VB.NET Application

I have an application which I've developed which queries Active Directory information and stores about 15 properties into a Datatable which is kept in memory.

I need to decrease the amount of "Commit" memory it is setting aside.

The application stays active in the system tray and allows for quick searching of information along with pictures for users.

I have a class, which is able keep memory usage down pretty low. It runs on a timer every 10 seconds and listed below:

Public Class MemoryManagement

    Private Declare Function SetProcessWorkingSetSize Lib "kernel32.dll" (ByVal process As IntPtr, ByVal minimumWorkingS开发者_StackOverflow中文版etSize As Integer, ByVal maximumWorkingSetSize As Integer) As Integer

    Public Shared Sub FlushMemory()
        GC.Collect()
        GC.WaitForPendingFinalizers()
        If (Environment.OSVersion.Platform = PlatformID.Win32NT) Then
            SetProcessWorkingSetSize(GetCurrentProcess().Handle, -1, -1)
        End If
    End Sub

End Class

After the application loads the Task Manager shows the following:

Working Set(Memory) - 30,000K

Memory(Private Working Set) - 13,000K

Commit Size - 25,000K

and after a few seconds the Memory Management class will reduce memory usage to:

Working Set(Memory) - 700K

Memory(Private Working Set) - 600K

Commit Size - 25,000K

One thing I've noticed is that the Commit Size never goes down and in fact will continue to grow (very slowly) over a few days. After two days it got up to 36,000K for the Commit Size.

Now I'm pretty positive I'm disposing all the objects that allow a dispose method and setting other objects to = nothing.

If I look at the Task Manager other applications don't have such a large footprint for the Commit Size.

Any ideas on how to further trim the commit size my application is setting aside?

Edit:

Per the suggestion below I've included some of the info from CLR Profiler below:

Summary for CSIDir.exe

Allocated bytes: 15,097,943

Relocated bytes: 3,680,460

Final Heap bytes: 1,612,611

Objects finalized: 16,194

Critical objects finalized: 148

Gen 0 collections: 19

Gen 1 collections: 17

Gen 2 collections: 16

Induced collections: 16

Gen 0 Heap bytes: 769,019

Gen 1 Heap bytes: 156,141

Gen 2 Heap bytes: 947,492

Large Object Heap bytes: 40,706

Handles created: 4,664

Handles destroyed: 4,386

Handles surviving: 278

Heap Dumps: 1

Comments: 0

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I suggest you to use profiler tools to see how your objects are actually allocated and destroyed. One such profiler for VB.net is CLR profiler from MS. The description of the profiler says:

The CLR Profiler includes a number of very useful views of the allocation profile, including a histogram of allocated types, allocation and call graphs, a time line showing GCs of various generations and the resulting state of the managed heap after those collections, and a call tree showing per-method allocations and assembly loads.