Introduction to ADO.NET Data service

Objective

This article will explain theoretical concept of ADO.NET Data Service.
Introduction:
• ADO.NET Data service framework provides an API that allows data to be created and consumed over HTTP using RESTful service.
• ADO.NET Data service supports all database operations using URI.
• ADO.NET Data service can expose an entity model via an URI.
• ADO.NET Data service is RESTful service to support CRUD operations on database.
• ADO.Net Data service could be consumed by any type of client like Windows, SilverLight, Web , AJAX and console.
So, ADO.NET Data service could be defined as,

It exposed all database operations as RESTful service on an entity model, if entity model supports both IUpdateable and IQueryable interface.

How HTTP Verbs being used ?

ADO.NET Data service uses HTTP to interact with data item using the HTTP Methods.

There are three options to make HTTP call.
1. By using Fiddler2
2. By using web browser’s address box
3. By client library. Client library exposed by the System.Data.Service.Client namespace. Client library encapsulates the HTTP Request such that developers have no need to manually craft HTTP Request.

Supported Message format

JSON message format is mainly to work with AJAX clients.
XML is highly readable message format.
ATOM is default message format. It is highly descriptive in nature.


Explanation of database , going to use forCRUD operation 

IPL database has been created. This contains three tables. Details of tables with records are illustrated below. 
Player_Information

Team_Information

Player_Team 

"Note: To accommodate URI query explained below , it is assumed that one ADO.NET DataService is added to the web project . To add ADO.NET Data Service, Right click on project and add new Item. ADO.Net Data Service works on an entity model. So To create Entity Model Add New Item and select Entity Model. Name of this entity model class will be used as base class for ADO.NET Service." 

How to create entity model and add ADO.NET services in a project. For step by step explanation, see my ADO.NET Services part 2 article on codegain.com

Querying using URI on database
On running service, following URI will get invoked by the browser.
http://localhost:2888/DataService.svc/

1. localhost:2888 is server and port number where service is running
2. DataService is name of ADO.NET data service.

Result would be in browser as below.

Above service is using ATOM message format 

Metadata
• One feature of ADO.NET data service is that, they provide operation to retrieve Metadata about the service and offer of the service.
• This is very useful in determining structure before requesting them.
• ADO.NET Data service provides metadata accessible.
• Metadata expose all the resource and custom services.
• Metadata could be accessed by appending $metadata to service URI.
So, the URI to access metadata is
http://localhost:2888/DataService.svc/$metadata
And metadata will be in browser as, the below is content in browser

URI Query options

Any complex query could we written using URI.
1. Below URI will display record from Player_Information table.
http://localhost:2888/DataService.svc/Player_Information

2. Below URI will display record from Team_Information table.
http://localhost:2888/DataService.svc/Team_Information 

URI options

URI logical operators

URI math operators

Examples : • Below query will fetch record of Team_Information with Team_Id equal to T2

http://localhost:2888/DataService.svc/Team_Information?$filter= TeamId eq 'T2' 

• Below query will fetch all records of Team_Information with Team_Id not equal to T2 

http://localhost:2888/DataService.svc/Team_Information?$filter= TeamId ne 'T2' 

• Below query will fetch top 2 records of Team_Information
http://localhost:2888/DataService.svc/Team_Information?$top=2
• Below query will fetch playerID P1 or P2 from Player_Information table.
http://localhost:2888/DataService.svc/Player_Information?$filter=(PlayerId eq 'P1') or (PlayerId eq 'P2')

Very Important Note:

1. ? $ URI Option = is used in all URI query to fetch records.

2. If Browser is unable to show the results of URI query make sure FEED Reading of browser is OFF. TO do so, in IE Browser click on TOOL-> Internet option -> Content. Select Feeds and Web slices setting. And uncheck Turn on reading view checkbox.

Access Rules

ADO.Net Data service class must inherit from DataService class.
Where, T is name of the entity model class.

public class DataService : DataService

Here IPLEntities is entity model class. DataService is name of ADO.NET Data service.
By default ADO.NET Data service disable all the access to entity model.
So it need to be enabled, such that client could access the entity model. Developer has explicitly give action to model to access.
SetEntitySetAccessRule(,) method is used to give access. This method accept two parameters.
1. Entity name on which rule to be applied.
2. Enumerator of EntitySetRight

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

This will permit all right access on all entity set.

config.SetEntitySetAccessRule("Player_Information", EntitySetRights.AllWrite);

This will permit all write access on Player_Information entity set. 

Creating the proxy class

There are two way to create proxy class for ADO.NET Data service at client side.
1. By adding service reference of ADO.NET Data service URI.
2. By using ADO.Net client library. To use client library there is need to add System.Data.Services.Client.dll assembly to the project. The two main constructs in the client library are the DataServiceContext class and the DataServiceQuery class.

Conclusion

Above article has explained theoretical concept of ADO.NET Data Service. For step to step explanation of how to create ADO.NET Data service and consume it in different type of clients,Happy Coding Thank you.