Lerman Vvs14 Ef Tips And Tricks

VVS14:Entity Framework Tips & Tricks
Julie Lerman
www.thedatafarm.com
jlerman@thedatafarm.com
twitter: @JulieLermanVT

Julie Lerman
website
theDataFarm.com
blog & twitter
theDataFarm.com/blog@julielermanVT
book web site
LearnEntityFramework.com
consultant/mentor
Microsoft MVP, INETA Speaker,ASPInsider, MCP, VTdotNET Leader

Tips & Tricks
Version 1 Pain Points Fixed in EF4
Query Helpers
Use ObjectQuery methods with LINQ to Entities
Find Exception Handling Details
Create Generic Queries
Encapsulate Query Execution
Improve Query Performance

!
V1 Model hides Foreign Key

Get FK value from Entity Reference

Set FK Value through Entity Ref
from Single EntityKey Property
Order.CustomerReference.EntityKey =
new EntityKey("MyEntities.Customers", "PersonID", 1)
from Multiple EntityKey Properties
vareKeyValues =
new KeyValuePair<string, object>[] {
new KeyValuePair<string, object>(“PropertyA", 12),
new KeyValuePair<string, object>(“PropertyB", 103)
};
EntityKey ekey= new EntityKey(“MyEntities", eKeyValues);
instance.EntityRef.EntityKey=ekey;

V1: Undesirable Store Queries
LINQ to Entities Query
From p In context.PeopleWhere p.LastName.StartsWith(“K")
Resulting T-SQL Query
SELECT [Extent1].[PersonID] AS [PersonID], ...
WHERE (CAST(CHARINDEX(N'T', Extent1].[LastName])
AS int)) = 1
!

Control Store Query with ESQL
Entity SQL
SELECT VALUE p FROM EFEntities.People AS p
WHERE p.LastName LIKE “T%”
Query Builder Methodscontext.People.Where("it.LastName LIKE 'T%'")
Resulting T-SQL
SELECT [Extent1].[PersonID] AS [PersonID],
WHERE [Extent1].[LastName] LIKE 'T%'

Queries in Entity Framework 4
Huge improvements to generated queries
Contains added to LINQ to Entities & ESQL
StartsWith, EndsWith,Contains LIKE %%
Much More..
See blogs.msdn.com/adonet
August 5, 2009 post

Awesome Third Party Tools
LINQPad
Test Queries
LINQ, L2S, L2E, ESQL
EFProf
Capture *All*
Database Activity

V1: Random columns from Sprocs
CREATE PROCEDURE OrdersBySalesPersonbyDate
AS
SELECT MIN(Person.FirstName) as First,
MIN(Person.LastName) as Last,
COUNT(OrderId) as OrderCount
FROM …
Requires lots of manual editing of the model, MSL and SSDL to create an entity that matches the return value
!

Use Views in Place of Sprocs
CREATE VIEW OrdersBySalesPersonbyDate
AS
SELECT MIN(Person.FirstName) as First,
MIN(Person.LastName) as Last,
COUNT(Orderid) as OrderCount
FROM …
Wizard creates all entity metadata elements
Other benefits
View is composable
Use in queries
Change Tracking (use stored procs for Ins/Upd/Del)

Stored Procs in Entity Framework 4
Major support improvements
Map functions to complex types
Designer can discover result shapes and auto-create the complex types for you

Country Reference List
List<Customer> GetCustomers()
{ return context.Customers.OrderBy(c => c.LastName)
.ToList(); }
Account Type Reference List
List<AccountType> GetAccountTypes()
{ return context.AccountTypes.OrderBy(a => a.TypeName)
.ToList(); }
Product Reference List
List<Product> GetProducts()
{ return context.Products.OrderBy(p => p. Name)
.ToList(); }
!
Redundant L2E Queries

Build Reusable, Generic Queries
public static List<TEntity> GetReferenceList<TEntity>
(this ObjectContext context)
context.GetReferenceList<Country>
context.GetReferenceList(Of AccountType)
context.GetReferenceList<Product>

Encapsulate Query Execution
Reusable Repository Methods
public List<TEntity> ExecuteList<TEntity>
(ObjectQuery<TEntity> objectQuery)
public List<TEntity> ExecuteList<TEntity>
(IQueryable<TEntity> L2EQuery)
Calling Reusable Methods
IEnumerable<Person> L2EQuery = from p in context.People
select p;
List<Person> people = dal.ExecuteList<Person>(L2EQuery);
ObjectQuery oQuery = context.Orders;
List<Order> orderList = dal.ExecuteList<Order>(oQuery);

s
Order B
?
Person A
Person B
Order A
db Error
?
Person D
Order C
?
Order D
Person C
!
UpdateExceptions Anonymity

ObjectStateEntry & Entity Instance provided in UpdateException

Pre-Compile L2E Queries
Pre-Compiled Query
LINQ to Entities
Query
Store
Query

Web Sites Lose Pre-Compiled L2E Queries
Short-lived ObjectContext used to compile
Pre-Compilation is repeated each time
App process loses benefit of pre-compilation
Big performance loss
!

Cache Pre-Compiled Query Func
Class Level Static Function
static Func<MyEntities, IQueryable<Customer>> customerPCQ;
Class Constructor
public CustomerProvider()
{
if (customerPCQ == null)
{
customerPCQ = CompiledQuery.Compile<MyEntities,
IQueryable<Customer>>
(ctx => from cust in ctx.Customers
where cust.Orders.Any()
select cust
);
}
}

Summary
Some of the big EFV1 pain points are gone in EF4
Don’t ignore the power of Entity SQL
Dig into the APIs to leverage the real power of EF

Julie Lerman
website
theDataFarm.com
blog & twitter
theDataFarm.com/blog@julielermanVT
book web site
LearnEntityFramework.com
consultant/mentor
Microsoft MVP, INETA Speaker,ASPInsider, MCP, VTdotNET Leader

Resources mentioned in this talk
Learnentityframework.com
Blogs.msdn.com/adonet,/efdesign, /alexj
www.linqpad.net
EF Profiler: http://ayende.com/Blog/category/551.aspx

Lerman Vvs14 Ef Tips And Tricks

by Julie Lerman on Nov 21, 2009

Accessibility

Categories

Tags

Upload Details

Usage Rights

1 Embed 19

Statistics

Lerman Vvs14 Ef Tips And Tricks — Presentation Transcript