The outline of the presentation (presented at NDC 2011, Oslo, Norway):
- Short summary of OData evolution and current state
- Quick presentation of tools used to build and test OData services and clients (Visual Studio, LinqPad, Fiddler)
- Definition of canonical REST service, conformance of DataService-based implementation
- Updateable OData services
- Sharing single conceptual data model between databases from different vendors
- OData services without Entity Framework (NHibernate, custom data provider)
- Practical tips (logging, WCF binding, deployment)
2. OData and REST
WCF Data Services
OData feed in 5 minutes: EF + MS SQL
The power of ObjectContext
Using reflection provider
Using custom providers and NoSQL
Extending OData services
Performance and diagnostics
A song about OData
3. Are you familiar with OData?
Have you used OData in your projects?
Do you have components on your machine
that use OData communication?
4. The Open Data Protocol (OData) is a Web
protocol for querying and updating data
Consumers query a datasource over HTTP
and get results back in formats like
AtomPub, JSON or plain XML
OData follows many of the principles of
REST
5.
6.
7.
8. Querying NuGet feed with LINQPad
Importing data from OData feed into
Microsoft Excel using PowerPivot
9. Command content specified in URIs
Use of HTTP verbs (GET, POST, PUT,
DELETE)
Use of HTTP status codes
Response sent as XML (AtomPub) or
JSON
Related content specified using link
elements
16. Request: a company with non-existing
CompanyName
Response: an empty collection
Request: a company with non-existing
CompanyID
Response: 404 Not Found
17. var ctx = new NorthwindContext("http://localhost.:50555/InMemory.svc");
ctx.IgnoreResourceNotFoundException = true;
var customers =
from c in ctx.Customers
where c.CustomerID == "XYZ"
select c;
18. Formerly ADO.NET Data Services
Codename “Astoria”
OData provider library for .NET
Not to be confused with WCF RIA Services
designed specifically for end-to-end
Silverlight and ASP.NET applications
19. Using Entity Framework provider
• EF model first+ MS SQL – trivial
• EF code first, different DB vendors – easy
Using reflection provider
• Any context exposing a set of IQueryable
properties – easy
• Implementing IUpdatable for updatable OData
feeds – easy
Using custom provider
• OData provider toolkit usually helps – still complex
20. public class EntityFrameworkModelFirstMsSql :
DataService<NorthwindMsSqlContext>
{
public static void InitializeService(DataServiceConfiguration config)
{
config.SetEntitySetAccessRule("*", EntitySetRights.All);
config.SetServiceOperationAccessRule("*", ServiceOperationRights.All);
config.DataServiceBehavior.MaxProtocolVersion =
DataServiceProtocolVersion.V2;
}
protected override NorthwindMsSqlContext CreateDataSource()
{
return new NorthwindMsSqlContext(/* connection string */);
}
}
21. As simple as with MS SQL assuming EF
provider for the respective vendor is
available
Proven choice: Devart dotConnect product
family:
• Oracle
• MySQL
• PostgreSQL
• SQLite
22. Not supported by tools
EDMX is just an XML file with 3 main
sections:
• Conceptual model (CSDL)
• Storage model (SSDL)
• Mapping (MSL)
You can author your own EF model:
• Support for n database vendors
• 2n + 1 XML sections (1 CSDL + n SSDL + n MSL)
23. DbContext class, wraps ObjectContext
Model is generated from entities
Database can be generated from the
model
Convention over configuration reduces
configuration code to bare minimum
No more trick to share conceptual model
between databases from different vendors
24. public class NorthwindContextBase : DbContext
{
public ObjectContext ObjectContext
{
get { return (this as IObjectContextAdapter).ObjectContext; }
}
}
public class EntityFrameworkCodeFirstMsSql : DataService<ObjectContext>
{
protected override ObjectContext CreateDataSource()
{
var ctx = new NorthwindContext("NorthwindContext.EF.CF.MsSql");
return ctx.ObjectContext;
}
}
25. Suitable for most of scenarios with static
resource set information (schema known
at compile time)
Resource sets exposed as IQueryable<T>
properties of the context class
DataServiceKey attribute specifies entity
key
Optional support for IUpdatable
27. Entity Framework provider is the quickest
way to add OData feed on the top of a
popular SQL database
Reflection provider covers most of other
scenarios when the data schema is known
up-front
Custom provider is needed when the
schema is discovered at runtime or data
don‟t have fixed types
28. If the content of NoSQL database is known
at compile time, reflection provider can be
used
If the content of NoSQL database is
divided into collections of fixed types, the
resource sets can be built at runtime
If the content is untyped, OData feed can
still be built using open types
29. Creating OData feed for MongoDB
using WCF Data Services
and OData Provider Toolkit
30. OData data model supports open types for
Entries. An entry of an open type may
have extra properties (dynamic properties)
in addition to those statically declared in
metadata
WCF Data Services framework takes care
of transforming the incoming requests into
an expression tree. Custom code is
responsible for evaluation expression tree
against the data store
31. Custom service operations can only use
HTTP GET and POST
Generated client context code does not
include custom service operations – it has
to be added manually
Default webHttpBinding settings may not
be sufficient for large payload
(send/receiveTimeout, maxBufferSize and
maxStringContentLength often need to be
increased)
32. [WebInvoke(Method = "POST")]
public void DeleteProductsByNamePattern(string namePattern)
{
this.CurrentDataSource.ExecuteStoreCommand(
string.Format("DELETE FROM Products WHERE
ProductName LIKE '{0}%'", namePattern));
}
34. OData design goal is to provide data
publishing protocol for services, not for
low-level components
Don‟t use OData to implement cascaded
updates and deletes of large number of
dependent entities
Understand the difference between client-
side and server-side operations
35. LINQPad (LINQ to OData)
Fiddler
RedGate .NET Reflector Pro (to step-in to
WCF Data Services code)
Oren Eini‟s profilers (EF Profiler,
NHibernate Profiler)
Elmah logging framework (install it using
NuGet, it will update your web.config)
36. Don‟t reinvent the wheel, don‟t come with
your own standards
Consider OData to expose data sources
on the Web
Don‟t treat OData as a SQL database
publisher
Writing OData feeds is easy
37. Code examples for this presentation:
https://github.com/object/
NorthwindOData
Open Data Protocol:
http://www.odata.org/
http://www.odata.org/mailing-list
WCF Data Services forum:
http://social.msdn.microsoft.com/Forums/e
n/adodotnetdataservices/
38. WCF Data Services Toolkit:
http://wcfdstoolkit.codeplex.com/
Microsoft WCF Data Services March 2011
CTP 2 for .NET Framework 4 and
Silverlight 4:
http://www.microsoft.com/downloads/en/de
tails.aspx?FamilyID=60fb0117-8cea-4359-
b392-6b04cdc821be
40. OData! Please relieve me
AtomPub is what I‟m gonna need
Believe me when I tell you:
AtomPub is what I‟m gonna need
41. OData! Please relieve me
JSON‟s what I want in JavaScript
Believe me when I tell you:
JSON‟s what I want in JavaScript
42. When you told me:
“Internal error 500”
Oh well you know,
I nearly broke down and cried
When you told me:
“Internal error 501”
Oh well you know,
I nearly broke down and died
43. OData! Please relieve me
I want to live a RESTful life
Believe me when I tell you:
I want to live a RESTful life
44. Vagif Abilov
Miles AS
vagif.abilov@gmail.com
@ooobject
github: object
http://bloggingabout.net/blogs/vagif/
