Re: Custom marshalling of ADO.NET dataset to ADO Recordset

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

Hi

Thank you both for the reply. I have seen examples showing this
transformation on the web. You may be interested to see
www.betav.com/msdn_magazine.htm (doing the impossible again).

However, I was not confident to use this method in a production environment
as I couldn't see where the schema for the recordset and dataset were
published, and the XSLT seemed to be written by inspection.

I came across the following article on MSDN but am having difficulty
implementing it. Any ideas?

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnbda/html/cominterop.asp,
In particular the section:
> >>
> >> "Another option is to write .NET custom marshaling code that
> >> automatically
> >> translates between a dataset and a recordset when a dataset is returned
> >> as a
> >> parameter. This is the most elegant solution and is transparent to the
> >> implementers of the business code in both tiers. "

Regards

Wayne

"Brendan Reynolds" wrote:

> As luck would have it, I just posted this yesterday ...
>
> http://groups.google.com/group/microsoft.public.access/msg/6c383918a1f33419
>
> --
> Brendan Reynolds
>
> "Matt Neerincx [MSFT]" <mattn@xxxxxxxxxxxxxxxxxxxx> wrote in message
> news:%23zIOE$o3FHA.3844@xxxxxxxxxxxxxxxxxxxxxxx
> > There is a very slick way to convert an ADO recordset to a .NET DataSet
> > (using OleDbDataAdapter) but not the other way around:
> >
> > http://www.c-sharpcorner.com/vbnet/vbcode/ADORecSetFromADONetMCB.asp
> >
> > So converting from DataSet to ADO Recordset is the hard one. Note that
> > one possible minimal code way to do this I can think of is to extract the
> > XML from the DataSet, then transform the XML to something that ADO
> > Recordset.Load will accept. So pass back XML to the client and have the
> > client transform the XML (so you offload the CPU to client). Have not
> > tried this myself but I feel it is theoretically possible.
> >
> > --
> > Matt Neerincx [MSFT]
> >
> > This posting is provided "AS IS", with no warranties, and confers no
> > rights.
> >
> > Please do not send email directly to this alias. This alias is for
> > newsgroup purposes only.
> >
> > "WayneB" <WayneB@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
> > news:3D2F93D9-0508-4767-AE5F-1ACB641D7004@xxxxxxxxxxxxxxxx
> >> Hi
> >>
> >> I hope someone can help with this - bit of a complicated problem.
> >>
> >> Our existing system is a COM based windows client, written in VB. There
> >> is a
> >> requirement for a server based solution and I have elected to use .NET,
> >> using
> >> Remoting for the communication between client and server and COM interop
> >> to
> >> bridge the VB6 client and .NET assemblies.
> >>
> >> In future, we hope to migrate our windows client to .NET but do not have
> >> the
> >> time or resource to do so at present.
> >>
> >> The problem is that I would like to use the .NET infrastructure and
> >> framework as far as possible, in particular using datasets and ADO.NET
> >> for
> >> data access. The problem comes when passing data back to the VB6 client.
> >>
> >> The client contains many screens hosting a 3rd party grid control, this
> >> expects a recordset. I have tried the simple approach of dynamically
> >> creating
> >> a recordset from a dataset (iterating through all rows in the dataset and
> >> adding to a disconnected recordset) but this takes far too long for a
> >> dataset
> >> containing large amounts of data.
> >>
> >> I came across this article
> >> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnbda/html/cominterop.asp,
> >> in particular the section:
> >>
> >> "Another option is to write .NET custom marshaling code that
> >> automatically
> >> translates between a dataset and a recordset when a dataset is returned
> >> as a
> >> parameter. This is the most elegant solution and is transparent to the
> >> implementers of the business code in both tiers. "
> >>
> >> I have created a custom marshaler in an attempt to convert the dataset to
> >> a
> >> recorset but cannot get VB6 to recognize the type as a recordset. I use
> >> the
> >> GUID attribute to type my implementation of a recordset as an
> >> ADODB.Recordset.
> >>
> >> i.e.
> >>
> >> <ComImport(), Guid("00000556-0000-0010-8000-00AA006D2EA4"),
> >> InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _
> >> Public Interface IMyRecordset
> >> Sub Open(Optional ByVal Source As Object = Nothing, Optional ByVal
> >> ActiveConnection As Object = Nothing, Optional ByVal CursorType As
> >> ADODB.CursorTypeEnum = ADODB.CursorTypeEnum.adOpenUnspecified, Optional
> >> ByVal
> >> LockType As ADODB.LockTypeEnum = ADODB.LockTypeEnum.adLockUnspecified,
> >> Optional ByVal Options As Integer = -1)
> >> Sub Close()
> >> Function GetRows(Optional ByVal Rows As Integer = -1, Optional ByVal
> >> Start As Object = Nothing, Optional ByVal Fields As Object = Nothing) As
> >> Object
> >> Property MaxRecords() As Integer
> >> Sub Move(ByVal NumRecords As Integer, Optional ByVal Start As Object =
> >> Nothing)
> >> Sub MoveFirst()
> >> Sub MoveLast()
> >> Sub MoveNext()
> >> Sub MovePrevious()
> >> ReadOnly Property RecordCount() As Integer
> >> Sub Requery(Optional ByVal Options As Integer = -1)
> >> Sub Resync(Optional ByVal AffectRecords As ADODB.AffectEnum =
> >> ADODB.AffectEnum.adAffectAll, Optional ByVal ResyncValues As
> >> ADODB.ResyncEnum
> >> = ADODB.ResyncEnum.adResyncAllValues)
> >> Sub Seek(ByVal KeyValues As Object, Optional ByVal SeekOption As
> >> ADODB.SeekEnum = ADODB.SeekEnum.adSeekFirstEQ)
> >> Property Sort() As String
> >> ReadOnly Property State() As Integer
> >> ReadOnly Property Status() As Integer
> >> Sub Update(Optional ByVal Fields As Object = Nothing, Optional ByVal
> >> Values As Object = Nothing)
> >> ReadOnly Property Fields() As ADODB.Fields
> >> Property DataMember() As String
> >> Sub AddNew(Optional ByVal FieldList As Object = Nothing, Optional
> >> ByVal
> >> Values As Object = Nothing)
> >> ReadOnly Property BOF() As Boolean
> >> ReadOnly Property EOF() As Boolean
> >> ReadOnly Property DataSource() As Object
> >> End Interface
> >>
> >> <ProgId("ADODB.Recordset")> _
> >> Public Class MyRecordset
> >> Implements IMyRecordset
> >> .... etc
> >>
> >>
> >> The VB program notes the type as MyRecordset and I can access methods,
> >> properties, etc. but the databind on the 3rd party control has no
> >> effect -
> >> presumably as it is not the correct type.
> >>
> >> I would be very grateful for any help - even if it's to tell me I'm
> >> wasting
> >> my time trying to get this to work.
> >>
> >> Best regards
> >>
> >> Wayne
> >
> >
>
>
>
.

Relevant Pages