Article ID: 238274 - Last Review: July 15, 2004 - Revision: 3.4

How To Obtain ObjectContext with ObjectControl Inside VB COM DLL From ASP and MTS

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SUMMARY

This article covers the implementation of the MTS ObjectContext through the ObjectControl inside a Visual Basic component under MTS control for ASP.
This is extremely useful if you would like to have direct access to the ASP intrinsic objects; for example, Application, Session, Response, Request, and Server.

In IIS 3.0, components access ASP built-in objects through the IScriptingContext interface. Components that need to access the built-in objects do so through page-level event methods. While this method is still supported, an alternative now exists and is recommended as an improvement over page-level event methods.

Instead, use the ObjectContext Object to access the built-in objects. ObjectContext makes IIS applications better suited for large-scale scenarios and provides support for transaction processing. It is highly recommended that you convert your existing ASP-based applications to this new approach if they are high-volume applications. This conversion is required if your applications support transaction processing.

Implement the ObjectControl interface when you want to define context-specific initialization and cleanup procedures for your MTS objects and specify whether or not the objects can be recycled.

The ObjectControl interface provides the following methods:

Activate: Allows an object to perform context-specific initialization whenever it's activated. This method is called by the MTS run-time environment before any other methods are called on the object.
CanBePooled: Allows an object to notify the MTS run-time environment of whether it can be pooled for reuse. Return True if you want instances of this component to be pooled, or False if not.
Deactivate: Allows an object to perform whatever cleanup is necessary before it's recycled or destroyed. This method is called by the MTS run-time environment whenever an object is deactivated.

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MORE INFORMATION

Create a new ActiveX DLL Project in Visual Basic.
Select References from the Project menu and add the following references to the project:
'Microsoft Transaction Server Type Library' (MTXAS.DLL)
'Microsoft Active Server Pages Object Library' (ASP.DLL)
Name the Project ObjectCtxtProject and name the Class ObjectCtxtClass.
Set the Class Property MTSTransactionMode = 1 - NoTransactions.

Copy and paste the following code into the Class Module:

Implements ObjectControl
Private objContext As ObjectContext
Option Explicit
Private Sub ObjectControl_Activate()
    ' Get a reference to the object's context here,
    ' so it can be used by any method that may be
    ' called during this activation of the object.
    Set objContext = GetObjectContext()
End Sub
Private Function ObjectControl_CanBePooled() As Boolean
    ' This object should not be recycled,
    ' so return false.
    ObjectControl_CanBePooled = False
End Function
Private Sub ObjectControl_Deactivate()
    ' Perform any necessary cleanup here.
    Set objContext = Nothing
End Sub

Copy and paste the following public method into the Class Module:

Public Sub TestMethodObjectCtxt()
    Dim objResponse As Response
    Dim objRequest  As Request
    
    Set objResponse = objContext("Response") ' Obtain ASP Response object
    Set objRequest  = objContext("Request")  ' Obtain ASP Request  object
    
    If InStr(objRequest.ServerVariables("HTTP_USER_AGENT"), "MSIE") > 0 Then
        objResponse.Write "You are using a very powerful browser."
    Else
        objResponse.Write "Try Internet Explorer today!"
    End If
End Sub

Compile the DLL.
Add the DLL to a MTS Server/Library Package.

Copy and paste the following ASP script into a new ASP file in a virtual directory.

<%
  set obj = Server.CreateObject("ObjectCtxtProject.ObjectCtxtClass")
  obj.TestMethodObjectCtxt
  set obj = Nothing
%>

Request the ASP file from a browser, you will see the following result if you are running Internet Explorer:
You are using a very powerful browser.
Otherwise you will see the following result:
Try Internet Explorer today!