The Open Grid Service Infrastructure (OGSI) has been designed to facilitate the creation of multiple, interoperable Grid service hosting environments, but to date only one fully OGSI-compliant hosting environment exists, Globus Toolkit version 3 (GT3). This paper describes the design and implementation of OGSI.NET, which is the second, independent hosting environment that is fully compliant with the OGSI specification. While the Microsoft suite of Visual Studio, Internet Information Services (IIS), and the Web Services Enhancements (WSE) provide a robust foundation upon which we implemented OGSI.NET, the challenges included constructing the Grid service container, parsing OGSI WSDL ("gwsdl"), and supporting Grid service handles (GSH). By describing our approach to these challenges, and by describing the unique Grid attribute programming. model we are developing as part of OGSI.NET, we contribute an early evaluation of OGSI and the broader Open Grid Services Architecture (OGSA).