Using Microsoft Entity Frameworks to Access Oracle Schema Objects with Virtuoso

This document details the steps required to provide Microsoft Entity Framework access to Oracle Schema Objects using the OpenLink Virtuoso Universal Server. This is achieved by linking the required Oracle 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 Oracle Schema objects linked into the Virtuoso Server.

Prerequisites

The following prerequisites must be in place for this solution to be possible.

Oracle DBMS

An Oracle DBMS hosting the required Schema Objects needs to be available. In this document, the Oracle Human Resources sample database will be used to demonstrate the process.

ODBC Driver for Oracle

An Oracle ODBC Driver is required for Linking the Oracle Schema Objects into the Virtuoso Server. The OpenLink ODBC Driver for Oracle will be used in this document, for which a functional ODBC Data source name of ora10ma will be assumed to exist on the machine hosting the Virtuoso Server.

Virtuoso Universal Server

A Virtuoso installation including the Virtuoso Universal Server and ADO.NET Entity Framework Provider is required. The Virtuoso components used must be Release 5.10.x or above, this being the minimum version containing support for Microsoft Entity Frameworks.

Microsoft Visual Studio 2008 SP1

Microsoft Visual Studio 2008 Service Pack 1 is required, this being the only version containing the necessary Entity Framework support available at the time of writing.

Tasks

Ensure Oracle Primary Keys (PKs) are not nullable

The Visual Studio 2008 Entity Data Model (EDM) requires that all primary keys are NOT Nullable and will fail to generate an EDM if any are. Thus, ensure any tables to be used are defined as not nullable in the Oracle database schema before attempting to generate an EDM. In the case of the Oracle Human Resources database, no primary keys are nullable. Therefore, this should not be an issue in this case.

Install and configure OpenLink ODBC Driver for Oracle

The Virtuoso Virtual Database engine uses ODBC as the connectivity mechanism for linking remote database objects into its local schema. Thus, an Oracle ODBC Driver must be available with a suitably configured DSN for connecting to the target database. The OpenLink ODBC Drivers for Oracle have been used in this document, although in theory any Oracle ODBC Driver can be used.

Installation instructions for the OpenLink ODBC Driver for Oracle are available from:

Install and configure OpenLink Virtuoso Universal Server

Linking Oracle tables into Virtuoso

Creating Visual Studio hosted Entity Data Model (EDM)

Using EDM to create Entity Framework based applications

Now that a Microsoft Entity Data Model has been created for the Oracle Human Resources database, Entity Framework applications can be created to make use of it.

Entity Frameworks based ADO.NET Data Service
Visual Studio Windows Form Application
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