SqlDataSource and npsql

Hi all,
since a while I try to configure npgsql as a .NET data provider for
SqlDataSource control in Visual Studio 2008 prof..
Npsql does not appear in the drop down list of data providers.

I have done the following configurations:

machine.config:
<DbProviderFactories>
<add name="Npgsql Data Provider" invariant="Npgsql" support="FF" description=".Net Framework Data Provider for Postgresql Server" type="Npgsql.NpgsqlFactory, Npgsql, Version=2.0.6.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7"/>
</DbProviderFactories>

web.config (C:\Windows\Microsoft.NET\Framework\v2.0.50727\CONFIG):
<connectionStrings>
<add name="DbVerbindung" connectionString="Server=localhost;Port=5432;Database=dbname;User Id=userid;Password=dbpassword"/>
</connectionStrings>

Is the error on my side or is it impossible what I am trying to do?
See also pgFoundry feature request "[#1000654] Add Support for SqlDatasource in ASP.NET 2.0".

Thanks a lot for any help on this.
Best Regards

Oliver