Entity Framework v2 Best Practices

Entity framework v2Best Practices
Microsoft Innovation Day 2010, May 11, 2010
AndriYadi| a@dycode.com
CEO, DyCode | MVP, VSTO

http://itunes.com/apps/movreak

JSON
WCF Data Services
HTTP/REST
Entity Framework
Real-world Scenario
SQL Server 2008

Dr. EF. Codd

INSERT
UPDATE
SELECT
DELETE
WHERE
HAVING
ORDER BY
Then we code in SQL
RIGHT
JOIN
COUNT
UNION
MIN/MAX
LEFT

ADO.NET code
SqlCommandoCmd;
SqlDataReaderoDR;
string connString = ConfigurationManager.
ConnectionStrings["OracleConnString"].
ConnectionString;
SqlConnectionconn = new SqlConnection(connString);
string selectQuery;
int _returnValue = 0;
selectQuery= “SELECT COUNT(OrderID) from Orders“ + “where EmployeeID=@EmpID”;
conn.Open();
oCmd= new SqlCommand(selectQuery, conn);
oCmd.Parameters.Add(“@EmpID”, SqlDbType.Int);
oCmd.Parameters[“@EmpID”].Value = employeeID;
oDR= oCmd.ExecuteReader();
if (oDR.Read())
_returnValue = oDR.GetInt32(0);
oDR.Close();
conn.Close();

The Dilemma
Software Architects & Developers
Database Designers & Administrators

ADO.NET
ADO
(1996)
DAO
(1992)
RDO

Enough! We need ORM!

Object Relational Mapping
Technique for working with relational tables as if they were objects in memory
Hide away the complexity of the underlying tables and give a uniform way of working with data

Why ORM?
Development productivity
Database independence
Database portability

Many attempts
Typed Datasets
Objectspaces ‘v1’
Objectspaces ‘v2’
Microsoft Business Framework
WinFS
Linq to SQL
NHibernate
 Will “RIP”
 Not Microsoft’s

ADO.NET Entity Framework
Microsoft’s strategic technology
Used in other Microsoft technologies (reporting services)
V2 released with .NET 4.0
14

Entity Data Model
Invented in the 1970s, by Dr. Peter Chen
ERM
Conceptual Layer
Mapping Layer
Storage Layer
Now: EDM in ADO.NET Entity Framework

Entity Framework vsLinqToSQL

Let’s go deeper on EF2

IEnumerable<T>
LINQ to Entities
Entity SQL Query
Entity Framework
EDM
EntityDataReader
Command Tree
Entity SQL Query
Conceptual Model
Mapping
Entity Framework
EntityDataReader
Command Tree
Storage Model
Entity Framework

Demo
Model-first

Eager Loading
Structure the initial query in such a way that all of the required objects are returned in the initial query
from c in nw.Customers.Include("Orders")select c;

Explicit Loading
Explicitly request to load the related objects
customer.Orders.Load();

Lazy Loading
Related objects are loaded automatically for you when you access them

POCO Support
Plain Old CLR Object
User your own POCO objects with no EF attributes
Code your POCO classes
Code Entity Framework Context
Or use T4 POCO entity generator by VS2010

Questions on POCO
Do I still need an EDM? Yes
How is metadata mapped to POCO entities? Convention based mapping
Entity Type, Property, and Complex Types names must match those defined by in EDM
Is deferred/lazy loading supported? Yes

Lazy Loading on POCO
Declare lazy-loaded property as virtual
Make sure to enable ContextOptions.LazyLoadingEnabled
What’s under the hood?

POCO Change tracking
Snapshot-based
Proxy-based

Demo
POCO

Demo
Generate EDM from database

Performance & security?
Connections to database vs. amount of data
You can work with stored procedures
You can work with views
You can define how the ADO.NET Entity Framework loads your data to
Eager
Lazy
(Explicit)

EF v2 in Distributed System

A WCF Service
Proxy
Data Binding
Entity Framework
ObjectContext available
ObjectContext not available
Distributed system – WCF service
SQL Server 2008

JSON/
XML
HTTP/REST
WCF Data Service
DataServiceContext
Data Binding
HTTP/REST
Entity Framework
ObjectContext available
ObjectContext not available
Distributed system – WCF Data service
SQL Server 2008

So, WHAT’s NEW in EF2?

Entity enhancements
Foreign-keys supported in the conceptual model
Testability enhancements
IObjectSet<T> and ObjectSet<T>
Easier to mock data context and data entities for tests
Lazy loading for related objects
Options now for explicit or implicit loading

Support for persistence ignorant objects
Persistence ignorant objects
POCO objects with no EF attributes, etc.
Mapped to conceptual model via convention
Change tracking possible with generated proxies or snapshot
Managing types in n-tier applications
Easier to add/attach objects to a context
More control over object state
Issues you should consider
You still need the Entity Data Model (edmx)
To use objects with WCF – use ProxyDataContractResolver

Designer enhancements
Support for complex types
Singularization& pluralization
Model first development
Creates DDL for database based on your model
Designer extensibility
Influence the EDMX generation
Add visuals
Influence DDL creation

Code generation customization
Based on T4 templates
Included as of VS 2008
Runtime support, but not much design support
T4 and Entity Framework
T4 used to generate code from model
Create new T4 templates to use instead
Add validation logic
Create POCO objects

References
ADO.NET team blog – keep up with new features in Entity framework
http://blogs.msdn.com/adonet
ADO.NET C# POCO Entity Generator
ADO.NET C# Web Site POCO Entity Generator
WCF Data Services team blog
http://blogs.msdn.com/astoriateam

DyCode
www.dycode.com | office@dycode.com
Dynamic IT Solutions for Optimal Business Value

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Entity Framework v2 Best Practices

by Andri Yadi on May 12, 2010

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Entity Framework v2 Best Practices — Presentation Transcript