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---+ Using Microsoft ADO.Net Data Services with Virtuoso

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---++ Introduction:

The goal of Microsoft ADO.NET Data Services is to enable applications to expose data as a data 
service that can be consumed by web clients within corporate networks and across the internet. 
A data service is reachable via regular HTTP requests, using standard HTTP verbs such as GET, 
POST, PUT and DELETE to perform CRUD operations against the service. The payload format used 
by the service is controllable by the application, but all options are simple, open formats 
such as JSON and Atom/APP.

The use of web-friendly technologies make ADO.NET Data Services ideal as a data back-end for 
AJAX-style applications, Rich Interactive Applications and other applications that need to 
operate against data that is stored across the web.

---++ Getting Started: Creating Data Services

---+++ Pre-requisites

In order to create a data service using ADO.NET Data Services  in your own environment you 
will need:

   1 Microsoft Visual Studio 2008 SP1, the ADO.NET Entity Framework runtime and associated 
tools are included in Visual Studio 2008 SP1.
   1 A running Virtuoso Universal Server instance.

---+++ Selecting a Data Source

The ADO.NET Data Service server framework is comprised of two halves. The top-half is the 
runtime itself; this part is ?fixed?, and it implements URI translation, the Atom/JSON wire 
formats, the interaction protocol, etc. This is what makes an ADO.NET Data Service look like 
an ADO.NET Data Service. The bottom half is the data-access layer and is pluggable. 
Communication between layers happens in terms of the IQueryable interface plus a set of 
conventions to map CLR graphs into the URI/payload patterns of ADO.NET Data Services.

The first step in creating an ADO.NET Data Service is to determine the data source that is 
to be exposed as a set of REST-based endpoints (i.e., select or create a data access layer).  
For relational data stored in Microsoft SQL Server or other 3rd Party databases, ADO.NET 
Data Services currently enables easily exposing a conceptual model created using the ADO.NET 
Entity Framework (EF).  For all other data sources (XML document, web service, application 
logic layer, etc) or to use additional database access technologies (ex. LINQ to SQL), a 
mechanism is provided which enables any data source, as per the plug-in model described 
above, to be exposed as an ADO.NET Data Service. 

To create a data service which exposes a relational database through an Entity Framework 
conceptual model see ?Creating a Data Service using the ADO.NET Entity Framework?. To 
create a data service which exposes another data source see ?Creating a Data Service from 
any Data Source?.          

---+++ Creating a Data Service using the ADO.NET Entity Framework

ADO.NET Data Services are a specialized form of Windows Communication Foundation services, 
and thus can be hosted in various environments. The below example will create an ADO.NET 
Data Service which is hosted inside an ASP.NET site. In order to create a data service, 
you must first create a web project; you will then need to establish a connection with 
the database that will be exposed by the service, and then create the data service itself 
within the web application. Below is a step-by-step description of this process.

The following steps can be used for creating a Data Service using the Virtuoso ADO.Net 
Provider for accessing the sample Northwind Demo database:

   1 Launch the Visual Studio 2008 SP1 IDE.
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   1 Create a <b>Web Application</b> project by going to the <b>File</b> menu in Visual 
Studio and choosing <b>New Project</b>. %BR%%BR%
   1 When the New Project window appears, choose either <b>Visual Basic</b> or 
   <b>Visual C#</b> as the programming language.%BR%%BR% 
   1 Within the language category click on <b>Web</b>, and select <b>ASP.NET Web 
Application</b> from the right-hand panel. %BR%%BR%
   1 Choose a name for the project, for example <b><nop>VirtuosoDataService</b>, 
and click <b>OK</b>.
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   1 This will create a new project called <b><nop>VirtuosoDataService</b>.
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   1 Right click on the <b><nop>VirtuosoDataService</b> project name of the 
<b>Solution Explorer</b> pane, then select the <b>Add</b> -> <b>New Item</b> 
menu options.
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   1 The <b>Add New Item</b> dialog will appear, choose the <b>ADO.NET Entity 
Data Model</b> template, give it the name <b>Virtuoso.edmx</b> and click <b>Add</b> 
to start the creation of the ADO.Net Entity Data Model.
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   1 In the <b>Entity Data Model Wizard</b> dialog <b>Choose Model Contents</b> 
page select the <b>Generate from Database</b> model type and click <b>Next</b>.
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   1 In the <b>Entity Data Model Wizard</b> dialog <b>Choose your Data Connection</b> 
page select the <b>New Connection</b> button
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   1 In the <b>Choose Data Source</b>dialog, select the <b>OpenLink Virtuoso Data 
Source</b> from the list displayed and click <b>Continue</b>.
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   1 In the <b>Add Connection</b> dialog, specify the <b>hostname</b>, <b>portno</b>, 
<b>username</b>, and <b>password</b> for the target Virtuoso Server and check the 
<b>Save Password</b> check box.
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   1 Select the <b>Select Database From List</b> radio button and choose <b>Demo</b> 
from the drop down list, assuming the Virtuoso Demo Database is installed.
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   1 Click the <b>Test Connection</b> button to verify the connection is successful 
and then click <b>OK</b> to add the connection.%BR%
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   1 Set the <b>entity connect string</b> name to <b>VirtuosoDemoEntities</b> (note 
this name as it is required in step 17 below) and click <b>Next</b>. 
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   1 In the <b>Choose your Database Objects</b> page select the <b>Tables</b> check 
box to select all tables in the Demo database for addition to the Entity Data Model, 
set the <b>Model Namespace</b> to <b>VirtuosoDemoModel</b> and click <b>Finish</b>.
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   1 The <b>Virtuoso.edmx</b> EDM will be created with the tables and relationships 
displayed in the Visual Studio IDE
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   1 Right click on the <b><nop>VirtuosoDataService</b> project name of the 
<b>Solution Explorer</b> pane, then select the <b>Add</b> -> <b>New Item</b> 
menu options.
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   1 The <b>Add New Item</b> dialog will appear, choose the <b>ADO.NET Data Service</b> 
template, give it the name <b>Virtuoso.svc</b> and click <b>Add</b> to create the 
ADO.Net Data Service.
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   1 In the <b>Virtuoso.svc.cs</b> Data Service file created add the data source 
class name of <b>VirtuosoDemoEntities</b> (note this is the name set in step 12) 
as the <b>DataService</b> name and enable the access to the Data Service by adding 
the entry <b>config.SetEntitySetAccessRule("*", EntitySetRights.All);</b> in the 
<b>InitializeService</b> method. 
<verbatim>
// C#

using System;
using System.Web;
using System.Collections.Generic;
using System.ServiceModel.Web;
using System.Linq;
using System.Data.Services;

namespace SimpleDataService
{
    public class Northwind : DataService<VirtuosoDemoEntities>
    {
        public static void InitializeService(IDataServiceConfiguration  config)
        {
            config.SetEntitySetAccessRule("*", EntitySetRights.All);
        }
    }
}
</verbatim>
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   1 To test the Data Service, simply hit <b>Ctrl+F5</b> within Visual Studio, which 
will start the development web server, run the Data Services server inside and load 
a Web browser page displaying the list of available tables/entities of the Demo 
database.  
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   1 To access a specific entity instance like the <b>Customers</b> table <b>ALFKI</b> 
record, this would be specified as 
<b><code><nowiki>http://host/vdir/Virtuoso.svc/Customers('ALFKI')</nowiki></code></b>.
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---++ NOTES

   1 <b>Important</b> - To view <b>Atom</b> (the default format returned by an ADO.NET 
Data Service) in Internet Explorer, you must first ensure that <b>Feed Reading View</b> 
is turned <b>off</b> . This can be done on the <b>Content tab</b> of <b>Tools<b> in 
<b>Internet Options</b>.%BR%%BR%
   1 If a Data Services entity instance URI page fails to load you can turn <b>Verbose</b> 
errors on by adding <b>config.UseVerboseErrors = true;</b> in the 
<b><code><nowiki>virtuoso.svc.cs InitializeService</nowiki></code></b> method to obtain 
more detailed information from the server as to why the page failed to load:
<verbatim>
public static void InitializeService(IDataServiceConfiguration config)

{

config.UseVerboseErrors = true;

config.SetEntitySetAccessRule("*", EntitySetRights.All);

}
</verbatim>