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Forum: General Questions
Topic: HOW TO: Using our ActiveX controls in a .NET service

Tony Priest

From: Utica, NY USA
Posts: 8466
Member Since: 04/11/00

posted October 14, 2004 9:49 AM

This "How to" applies to using our ActiveX controls in a .NET service. Note that this problem does not occur with our .NET components.

Due to the way messages are processed in a .NET service, you need add an Idle loop so that messages are processed after the server starts.

Here is how to do it in VB:

Add the following to the top of your main code file:

  Public Delegate Sub IdleDelegate()
  Private bStarted As Boolean

Add this to the beginning of your OnStart event:

  Dim o() As Object
  Dim i As New IdleDelegate(AddressOf Idle)
  i.BeginInvoke(New AsyncCallback(AddressOf DoNothingCallBack), o)

Add this to the end of your OnStart event:

  bStarted = True

Add this to your OnStop event:

  bStarted = False

Add the following subroutines:

  Protected Sub Idle()
    While bStarted = True
      MessageProcessing.Idle()
    End While
  End Sub

  Private Sub DoNothingCallBack(ByVal ar As IAsyncResult)

  End Sub

Lastly, create a new module called "MessageProcessing.vb" and add the following code:

Module MessageProcessing
  Private Const WM_APP = &H8000
  Private Const M_ADDRESS_EVENT = WM_APP
  Private Const M_CLOSE_EVENT = WM_APP + 2

  Private Structure POINTAPI
    Public x As Integer ' X-Coordinate in pixels
    Public y As Integer ' Y-Coordinate in pixels
  End Structure

  Private Structure MSG
    Public hWnd As IntPtr    ' Window handle of the associated window
    Public Message As Integer ' Message identifier
    Public wParam As IntPtr  ' Additional message info
    Public lParam As IntPtr  ' Additional message info
    Public time As Integer   ' Time message was posted
    Public pt As POINTAPI    ' Cursor position when message was posted
  End Structure

  Private Declare Auto Function GetMessage Lib "user32" _
    (ByRef lpMsg As MSG, _
     ByVal hWnd As IntPtr, _
     ByVal wMsgFilterMin As Integer, _
     ByVal wMsgFilterMax As Integer) As Boolean

  Private Declare Function TranslateMessage Lib "user32" _
    (ByRef lpMsg As MSG) As Boolean

  Private Declare Auto Function DispatchMessage Lib "user32" _
    (ByRef lpMsg As MSG) As IntPtr

  Private Declare Auto Function PeekMessage Lib "user32" _
    (ByRef lpMsg As MSG, _
     ByVal hWnd As Long, _
     ByVal wMsgFilterMin As Long, _
     ByVal ByValwMsgFilterMax As Long, _
     ByVal wRemoveMsg As Long) As Long

  Public Function Idle() As Boolean
    Dim Msg As New MSG
    If GetMessage(Msg, Nothing, M_ADDRESS_EVENT, M_CLOSE_EVENT) Then
      TranslateMessage(Msg)
      DispatchMessage(Msg)
      Return True
    End If
    Return False
  End Function
End Module

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