Programmer's Guide:
Programming Guidelines and Recommendations

 

Building ASP Pages using eRoom SAAPI

  • Never hold onto eRoom objects or interfaces across ASP page requests. That is, don't store objects or interfaces in session or application variables. Always release an object or interface before the end of an ASP page.

  • Pages should be run from a virtual root that is configured to run in the IIS process along with eRoom. Ensure that the application protection is set to low (IIS Process).

  • In some cases, when using SAAPI in ASP, you might need to ensure that eRoom's storage subsystem remains loaded. Do this by storing an IERUApplication (eRoom.Application) either in the user's session, or in an ASP application object in global.asa. Note that this is the only eRoom object/interface that should ever be stored on the session or in application-scope objects. This is to ensure that database connections are not held open. (See example)

  • eRoom's IIS virtual roots must allow anonymous login and not contain basic authentication or Windows Integrated Security. This includes any directories below /eRoomASP/Extensions/, as they are part of the eRoom application.

Building Visual Basic .DLLs

When building Visual Basic .DLLs for IIS or COM+ environments, you should always ensure that the Unattended Execution and Retain in Memory options are selected.   If these options are not selected, the Visual Basic runtime unloads custom and runtime .DLLs unexpectedly, which causes the computer to stop responding (crash or hang) under some multithreaded scenarios.

Follow these steps to enable these options in your Visual Basic project:

1. From the Project menu, select Project Properties.

2. On the General tab, select the Unattended Execution and Retain In Memory checkboxes.

The Unattended Execution option is not available if the project contains any user interface elements, such as forms or controls. The Retain in Memory option is not available if Unattended Execution is not selected.

Prior to Service Pack 3 for Visual Studio 6.0, it was possible to receive an access violation during process shutdown with Retain in Memory enabled. This has been fixed Visual Studio 6.0, Service Pack 3 or later.

Releasing Deleted Objects

If you delete an object through SAAPI code, that object is not deleted from the eRoom Server until all references to it are released.  This includes any collections in your application that may contain the deleted item.  Your application may behave unexpectedly if you try to create another item by the same name without releasing all references to the deleted item.  The following example illustrates this error.

Sub Main

Const const_FacilityName = "sample"

Const const_TemplateRoomPrefix = "template_"

Dim App

Dim facility

Dim rooms

Dim room

Set App = CreateObject("eRoom.Application")

Set facility = App.GetFacility(const_FacilityName)

Set rooms = facility.rooms

'# Find all rooms that start with the phrase "template_"  Make a fresh copy of those rooms.

For Each room In rooms

        If lcase(left(room.urlname, Len(const_TemplateRoomPrefix))) = lcase(const_TemplateRoomPrefix) Then
             '## Recreate room; (See explanation below.)

            Call RecreateTemplateRoom(facility, room, Mid(room.urlname, Len(const_TemplateRoomPrefix) + 1) )

        End If

Next

End Sub

Sub RecreateTemplateRoom(facility, room, roomname)

'# The roomname variable contains the name of the template room with the "template_" prefix removed.

    Dim newroom    

    Set newroom = Nothing

    Set newroom = facility.GetRoomByName(roomname)

    '# If a room by that name already exists, then delete it.    

    If Not (newroom Is Nothing) Then

        newroom.Delete

        Set newroom = Nothing

    End If

'# More code to recreate the room based on the template room.

'#  ...

End Sub

In the RecreateTemplateRoom subroutine, we set the newroom variable to Nothing after deleting the room, releasing that reference to the object. However, there is a second reference to that room inside of the rooms collection variable in the Main subroutine. Because the rooms collection has not yet been released, the room that was referenced by the newroom variable has not been deleted from the eRoom Server. This will create unexpected behavior if you were to try to create a room of the same name as the deleted room.