Using Microsoft Entity Frameworks to Access PostgreSQL Schema Objects with Virtuoso

This document details the steps required to provide Microsoft Entity Framework access to PostgreSQL Schema Objects using the OpenLink Virtuoso Universal Server. This is achieved by linking the required PostgreSQL Schema objects into Virtuoso using its built-in Virtual Database engine, and then using the Virtuoso ADO.NET Entity Framework provider to query the remote PostgreSQL Schema objects linked into the Virtuoso Server.

Prerequisites

The following must be in place to complete this exercise.

1. Microsoft Visual Studio 2008 SP1 (or later)
   Microsoft Visual Studio 2008 Service Pack 1 (or later) is required, as previous versions do not include the necessary Entity Framework support.
   
   
2. Virtuoso ADO.NET Entity Framework Provider, v5.10 or later
   The ADO.NET Entity Framework Provider must be installed on the Visual Studio development and deployment host(s). Version 5.10.x or later is required, as previous versions do not include the necessary Entity Frameworks support.
   
   
3. Virtuoso Universal Server, v5.10 or later
   Virtuoso Universal Server Release 5.10 or later is required, as previous versions do not include the necessary Entity Frameworks support. This may be on any host which is TCP/IP accessible from the Visual Studio development and deployment host(s).
   
   
4. ODBC Driver for PostgreSQL
   The Virtuoso Server uses an ODBC Driver for PostgreSQL to link in the PostgreSQL Schema Objects. The OpenLink Single-Tier ODBC Driver for PostgreSQL will be used in this document, and a functional ODBC Data Source Name (DSN) of "pgr8ma" will be assumed to exist on the machine hosting the Virtuoso Server. Any ODBC compliant driver for PostgreSQL should work.
   
   
5. PostgreSQL DBMS
   A PostgreSQL DBMS hosting the required Schema Objects needs to be available. This may be on any host which is TCP/IP accessible from the Virtuoso Server host. In this document, a Northwind database imported into PostgreSQL database will be used to demonstrate the process.
   
   

Tasks

1. Ensure PostgreSQL Primary Keys (PKs) are not nullable
   The Visual Studio 2008 Entity Data Model (EDM) requires that all primary keys are NOT Nullable. Visual Studio 2008 will fail to generate an EDM if any are. Therefore, ensure any primary keys to be used are defined as not nullable in the PostgreSQL database schema before attempting to generate an EDM. In the case of our PostgreSQL Northwind database all primary keys are non nullable. Thus, this should not be an issue in this case.
   
   
2. Install and configure the OpenLink ODBC Driver for PostgreSQL
   
   
3. Install and configure OpenLink Virtuoso Universal Server
   
   
4. Link PostgreSQL tables and other schema objects into OpenLink Virtuoso
   
   
5. Create a Visual Studio-hosted Entity Data Model (EDM)
   
   
6. Use the EDM to create an Entity Frameworks-based ADO.NET Data Service
   
   
7. Use the EDM to create an Entity Frameworks-based Windows DataGrid Form Application
   

CategoryDocumentation CategoryVirtuoso CategoryEntityFrameworks CategoryDotNET CategoryPostgreSQL