INTER PROCESS COMMUNICATION USING REGISTERMESSAGE and POSTMESSAGE

Public Class clsIPC
    Inherits System.Windows.Forms.NativeWindow
    Implements IDisposable

    Private Const GLOBAL_IDENTITY_ONE = "GLOBAL_IDENTITY_ONE"
    Private Const GLOBAL_IDENTITY_TWO = "GLOBAL_IDENTITY_TWO"

    Private Const MESSAGE_FOR_ONE = "MESSAGE_ONE"
    Private Const MESSAGE_FOR_TWO = "MESSAGE_TWO"


#Region "API Declaration"

    'API function to create custom system-wide Messages
    Private Declare Function RegisterWindowMessage Lib "user32" Alias "RegisterWindowMessageA" _
        (ByVal lpString As String) As IntPtr

    'API function to find window based on WindowName and class
    Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
        (ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr

    'API function to send async. message to target application
    Private Declare Function PostMessage Lib "user32" Alias "PostMessageA" _
        (ByVal hwnd As IntPtr, ByVal wMsg As IntPtr, ByVal wParam As Integer, _
        ByVal lParam As Integer) As IntPtr

#End Region

    Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
        Select Case m.Msg
            Case TWO_TO_ONE_MESSAGEID().ToInt32
                MessageBox.Show("GOT A MESSAGE FROM ONE--- CALLING METHOD A", "VBNETMessaging")
                Call A()
        End Select
        MyBase.WndProc(m)
    End Sub

    Private Sub A()
        MsgBox("Message from Method A")
    End Sub
    Public ReadOnly Property TWO_TO_ONE_MESSAGEID() As IntPtr
        Get
            Static objTWO_TO_ONE_MESSAGEID As IntPtr

            If IntPtr.Zero.Equals(objTWO_TO_ONE_MESSAGEID) Then
                objTWO_TO_ONE_MESSAGEID = RegisterWindowMessage(MESSAGE_FOR_TWO)
            End If
            Return objTWO_TO_ONE_MESSAGEID
        End Get
    End Property


#Region "dispose method and new()/constructor"

    Public Sub Dispose() Implements IDisposable.Dispose
        If Not Me.Handle.Equals(IntPtr.Zero) Then
            Me.ReleaseHandle()
        End If
    End Sub

    Public Sub New()
        '''''Creating Window based on globally known name, and create handle
        '''''so we can start listening to Window Messages.
        Dim Params As CreateParams = New CreateParams
        Params.Caption = GLOBAL_IDENTITY_TWO
        Me.CreateHandle(Params)
    End Sub
#End Region

End Class