Transcript Entity SQL Block

© Copyright SELA software & Education Labs Ltd. 14-18 Baruch Hirsch St.Bnei Brak 51202 Israel
www.sela.co.il
© 2009 Gil Fink. All rights reserved.
Entity Framework
Introduction
Exploring the Entity Data
Model
Querying and Manipulating
Entity Data Models
Customizing Entity Data
Models Examples
EF4
Summary
© 2009 Gil Fink. All rights reserved.
• The “Impedance Mismatch”
Relational
Database
© 2009 Gil Fink. All rights reserved.
Conceptual /
Business Model
(Objects)
• Data access framework
• Supports data-centric applications and services
• Enables programming against a conceptual application
model
• Enables independency of any data storage engine or
relational schema
© 2009 Gil Fink. All rights reserved.
•
•
•
•
EF uses a model called an Entity Data Model (EDM)
EDM is a client-side data model
EDM is an abstraction layer on top of the data storage
Remove the pain of
– Interacting with the data storage
– Translating the data into objects
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
• Items described in the EDM are called entities
• Entities have only properties but no behavior
• Entities can have relationships with other entities
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
• The model doesn't have any knowledge of the data storage
• The backend data storage has no impact on your model or
your code
• Uses a provider model to interact with the data storage
• Available providers:
– SQL Server
– Oracle
– MySQL
– Many more
© 2009 Gil Fink. All rights reserved.
Entity Framework
Introduction
Exploring the Entity Data
Model
Querying and Manipulating
Entity Data Models
Customizing Entity Data
Models Examples
EF4
Summary
© 2009 Gil Fink. All rights reserved.
•
•
•
•
Automatically generates classes from the model
Takes care of all of the database connectivity
Provides common query syntax for querying the model
Provides a mechanism for tracking changes to the
model's objects
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
• Designer Window:
–
–
–
–
–
Graphical representation of an EDM and its members
Enables adding more features to the model
Enables properties configuration
Enables updating from the data store
Enables model validation
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
• The Three Parts of the Model:
The image is taken from Julia Lerman’s book Programming Entity Framework, 1st Edition
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
• EF automatically creates a set of classes from the model
• You work with the model through the generated classes
• Every change to the model can change the generated
classes
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
Entity Framework
Introduction
Exploring the Entity Data
Model
Querying and Manipulating
Entity Data Models
Customizing Entity Data
Models Examples
EF4
Summary
© 2009 Gil Fink. All rights reserved.
• Queries are built against a data model
• EDM query transform into data storage query
• Query results materialize into model entities
The image is
taken from
Julia Lerman’s
book
Programming
Entity
Framework,
1st Edition
© 2009 Gil Fink. All rights reserved.
• Three kinds of queries in EF
– LINQ to Entities
– Entity SQL with Object Services
– Entity SQL with Entity Client
• Every kind has its pros and cons
© 2009 Gil Fink. All rights reserved.
Queries written in LINQ syntax
Support for LINQ features
Full IntelliSense support
var courses = from course in context.Courses
where course.Title.StartsWith("C")
orderby course.Title ascending
select new
}
Title = course.Title,
Location = course.Location
};
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
T-SQL-like query language
Provide the necessary capabilities for querying the
EDM
EF translates Entity SQL into storage-specific queries
var qStr = @"SELECT VALUE c
FROM SchoolEntities.Courses AS c
WHERE c.Title=‘Calculus'";
var courses = context.CreateQuery<Course>(qStr);
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
Streams data back to the application
Resembles SqlClient, OracleClient and the other client
providers
using (var conn = new EntityConnection("name=ProgrammingEFDB1Entities"))
{
conn.Open();
var qStr = "SELECT VALUE c FROM SchoolEntities.Courses AS c ";
var cmd = conn.CreateCommand();
cmd.CommandText = qStr;
using (var rdr = cmd.ExecuteReader(CommandBehavior.SequentialAccess))
{
while (rdr.Read())
{
Console.WriteLine(rdr.GetString(1));
}
}
}
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
LINQ to Entities
Entity SQL with
Object Services
Entity SQL
with Entity Client
LINQ support
√
−
−
IntelliSense
√
−
−
Model dynamic
queries
−
√
√
Return type
Objects
Objects or
DbDataRecords
DbDataReader
Performance
√
√√√
√√
© 2009 Gil Fink. All rights reserved.
• Choose Entity SQL with Entity Client:
– You want to return streamed data
– You want to use EDM in existing applications
• Choose Entity SQL with Object Services:
– You want to express queries that LINQ doesn’t enable
– You want dynamic queries
– You want the best performance
• Otherwise choose LINQ to Entities
© 2009 Gil Fink. All rights reserved.
© Copyright SELA software & Education Labs Ltd. 14-18 Baruch Hirsch St.Bnei Brak 51202 Israel
www.sela.co.il
© 2009 Gil Fink. All rights reserved.
• Every entity in ObjectContext has a ObjectStateEntry
• ObjectContext uses ObjectStateEntries to track entity
changes
© 2009 Gil Fink. All rights reserved.
Persists back to the data storage all the changes made
to entities
Uses the ObjectStateEntries to build the relevant data
storage commands
Unit of work pattern
context.SaveChanges();
OR
// doesn’t refresh the entities state after save
context.SaveChanges(false);
© 2009 Gil Fink. All rights reserved.
Create entity in memory
Create in memory manually
Use one of the entity’s generated create methods
var department = new Department();
var course = Course.CreateCourse(…);
© 2009 Gil Fink. All rights reserved.
Add entity
By Assignment to an existing entity’s property
By adding to a EntityCollection using Add method
Use ObjectContext AddTo methods
course.Department = department;
department.Courses.Add(course);
context.AddToCourses(course);
© 2009 Gil Fink. All rights reserved.
• Change a property or reference to entity
• The changes will be tracked by the ObjectStateEntry
• A call to SaveChanges will create update command
© 2009 Gil Fink. All rights reserved.
Entity must be in hand in order to perform delete
Use the ObjectContext DeleteObject method
// course need to be at hand
context.DeleteObject(course);
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
• Map procedures directly to ObjectContext as methods
Sproc /
Function
Method
• Map procedures to entities
• Override automatically CUD behavior
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
Entity Framework
Introduction
Exploring the Entity Data
Model
Querying and Manipulating
Entity Data Models
Customizing Entity Data
Models Examples
EF4
Summary
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
• The inheritance tree is create through one table only
• TPH inheritance depends on conditional mapping
• The condition is used to define records as different
types
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
•
•
•
•
•
Are elements of the SSDL
Are created whenever you map a view into the EDM
Are a projection of data and therefore are read only
Using stored procedures you can add write functionality
You can create your own DefiningQueries
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
Entity Framework
Introduction
Exploring the Entity Data
Model
Querying and Manipulating
Entity Data Models
Customizing Entity Data
Models Examples
EF4
Summary
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
Database
First (v1)
Model
First (v4)
Existing
Database
Entity Data
Model
© 2009 Gil Fink. All rights reserved.
Entity Data
Model
Generated
Database
VS.
1) 1:1 DB Mapping
2) Could get “crowded”
3) No designer support
on V1
© 2009 Gil Fink. All rights reserved.
1) Flexibility from DB shape
2) Nicely “organized”
3) Designer supported
© 2009 Gil Fink. All rights reserved.
Class Definition
Everything
Navigation Property Definition
Scalar Property Definition
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
Get Product
2) Access
Category
Get Category
Database
3) Get Category
2) Access
Category
© 2009 Gil Fink. All rights reserved.
Get Product
Get Category
Database
Implicit
1) Get Product
Explicit
1) Get Product
In theory this
This
is perfect!
looks
really
good
In theory this also
looks really good
© 2009 Gil Fink. All rights reserved.
Entity SQL
Block
Umm, I’d rather be using LINQ…
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.
1) Get Product
Web Service
2) Update Product
2) Make
Changes
Combines power of:
1) DataSet
2) DTOs
© 2009 Gil Fink. All rights reserved.
Database
Entity Framework
Introduction
Exploring the Entity Data
Model
Querying and Manipulating
Entity Data Models
Customizing Entity Data
Models Examples
EF4
Summary
© 2009 Gil Fink. All rights reserved.
• Entity Framework brings massive changes to data access
area
• We only scratched the surface
• Entity Framework
–
–
–
–
Data access framework
Supports data-centric applications and services
Enables programming against a conceptual application model
Has many features to be discovered
© 2009 Gil Fink. All rights reserved.
• My Blog:
– http://blogs.microsoft.co.il/blogs/gilf
• ADO.NET Team Blog
– http://blogs.msdn.com/adonet
• Data Developer Center:
– http://msdn.microsoft.com/data
© 2009 Gil Fink. All rights reserved.
© 2009 Gil Fink. All rights reserved.