How to get ObjectContext to compile? - vb.net

Question

I'm converting some code from VB6 to VB.Net and it contains a number of occurrences of:-
Private m_myobj As ObjectContext
m_myobj = GetObjectContext()
' do stuff, then
m_myobj.SetAbort()
' or
m_myobj.SetComplete()
By dint of including a reference to System.Data and System.Data.Entity and Imports System.Data.Object I have managed to get the declaration to compile, but the others have so far resisted. The errors showing are:-
'GetObjectContext' is not declared. It may be inaccessible due to its protection level
'SetComplete' is not a member of 'System.Data.Objects.ObjectContext'
'SetAbort' is not a member of 'System.Data.Objects.ObjectContext'
It would appear from the documentation that the two methods don't actually exist but they (presumably) must have worked in the VB6. Does anyone know what I should do about this?

Answer 1

The SetAbort and SetComplete methods are calls out to the COM+ (Was once called MTS) application that the class is running in, and allow parts of the code to vote on whether distributed database transactions will be committed by the com+ environment. You will want to look at the code path and see whether the code is required or not. If it is you will want to investigate other methods of extending database transactions across multiple DB accesses. In my experience people sometimes got excited about this technology and implemented it unnecessarily and it is quite possible that you can just eliminate the code.
The simplest way to duplicate this functionality would be to maintain an open connection and call begintran and endtran appropriately, this kind of stuff tend to get complicated though.
I suppose the closest modern Microsoft equivilant is Entity Framework.

Answer 2

GetObjectContext is a Windows function. You can declare it using P/Invoke like this:
<DllImport("ComSvcs.dll", CallingConvention:=CallingConvention.Cdecl)> _
Public Shared Function GetObjectContext(<Out> ByRef pCtx As IObjectContext) As Integer
End Function
<ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("51372AE0-CAE7-11CF-BE81-00AA00A2FA25")> _
Public Interface IObjectContext
Function CreateInstance(ByVal rclsid As Guid, ByVal riid As Guid) As Object
Sub SetComplete()
Sub SetAbort()
Sub EnableCommit()
Sub DisableCommit()
<PreserveSig> _
Function IsInTransaction() As Boolean
<PreserveSig> _
Function IsSecurityEnabled() As Boolean
Function IsCallerInRole(<MarshalAs(UnmanagedType.BStr)> ByVal role As String) As Boolean
End Interface