orm - ivan marković

Ivan MarkovićMSP LeadSoftware Developer at SPAN d.o.o.ivan.markovic@studentpartner.com

Vidjeli smo…

• Tipovi aplikacija• Metode razvoja softverskog

proizvoda+ALM u Microsoft alatima• C#• Baze podataka

Agenda

1) Entity Framework2) LINQ3) EF+LINQ Demo(s)

Entity framework

What is Entity Framework?

• Entity framework is an Object/Relational Mapping (O/RM) framework

• Automated mechanism for accessing & storing the data in the database

What is ORM?

• ORM is a tool for storing data from domain objects to relational database (like MS SQL Server)

• O/RM includes three main parts: Domain class objects, Relational database objects and Mapping information

Why ORM?

• ORM allows us to keep our database design separate from our domain class design

• This makes the application maintainable and extendable

ORM vs Traditional Data Access Techniques

• ORM often reduces the amount of code that needs to be written

• High level of abstraction obscuring what is actually happening in the implementation code

Entity Framework Architecture

SQL Relationships

• One-to-Many Relationship• Many-to-Many Relationship• One-to-One Relationship

EF 6 Tools for VS 2012 & 2013

• http://www.microsoft.com/en-us/download/confirmation.aspx?id=40762

Database first

• An existing database can be used• Code can be auto-generated.• Extensible using partial classes/ T4 templates• The developer can update the database

manually• There is a very good designer, which sync

with the underlining database

Code first

• There is full control of the model from the Code; no EDMX/designer

• No manual intervention to DB is required

• The database is used for data only• POCO Class

Model first

• Good support with EDMX designer• We can visually create the database model• EF generates the Code and database script• Extensible through partial classes• We can modify the model and update the

generated database.

Code first from existing database

• POCO Classes from existing database

Which one to choose?

• It depends on you…

LINQ

• Language-Integrated Query (LINQ)• Set of features that extends powerful

query capabilities to the language syntax of C# and Visual Basic. 

LINQ

Three parts

• All LINQ query operations consist of three distinct actions:– Obtain the data source.– Create the query.– Execute the query.

Three parts• // 1. Data source. • int[] numbers = new int[7] { 0, 1, 2, 3, 4, 5, 6 };

• // 2. Query creation. • // numQuery is an IEnumerable<int> • var numQuery =• from num in numbers• where (num % 2) == 0• select num;

• // 3. Query execution. • foreach (int num in numQuery)• {• Console.Write("{0,1} ", num);• }

The Data Source

• Types that support IEnumerable<T> or a derived interface such as the generic IQueryable<T> are called queryable types

The Query

• The query specifies what information to retrieve from the data source or sources

• Query also specifies how that information should be sorted, grouped, and shaped before it is returned

• The query expression contains three clauses: from, where and select

Deferred execution

• query variable itself only stores the query commands

• The actual execution of the query is deferred until you iterate over the query variable in a foreach statement

Forcing Immediate Execution

• Examples of such queries are Count, Max, Average, and First. These execute without an explicit foreach statement because the query itself must use foreach in order to return a result.

• That these types of queries return a single value, not an IEnumerable collection.

• ToList<T>, ToArray<T>

LINQ vs SQL

SELECT UPPER(Name)FROM CustomerWHERE Name LIKE 'A%'ORDER BY Name

LINQ vs SQL

SELECT UPPER(Name) FROM( SELECT *, RN = row_number() OVER (ORDER BY Name) FROM Customer WHERE Name LIKE 'A%') AWHERE RN BETWEEN 21 AND 30ORDER BY Name

LINQ vs SQL

var query = from c in db.Customers where c.Name.StartsWith ("A") orderby c.Name select c.Name.ToUpper();

var thirdPage = query.Skip(20).Take(10);

LINQ vs SQL

from p in db.Purchaseswhere p.Customer.Address.State == "WA" || p.Customer == nullwhere p.PurchaseItems.Sum (pi => pi.SaleAmount) > 1000select p

LINQ vs SQLSELECT p.*FROM Purchase p LEFT OUTER JOIN Customer c INNER JOIN Address a ON c.AddressID = a.ID ON p.CustomerID = c.IDWHERE (a.State = 'WA' || p.CustomerID IS NULL) AND p.ID in ( SELECT PurchaseID FROM PurchaseItem GROUP BY PurchaseID HAVING SUM (SaleAmount) > 1000 )

When not to use LINQ for querying databases

• Hand-tweaked queries (especially with optimization or locking hints)

• Queries that involve selecting into temporary tables, then querying those tables

Query syntax vs Method syntax

• IEnumerable<int> numQuery1 =

• from num in numbers

• where num % 2 == 0

• orderby num• select num;

• IEnumerable<int> numQuery2 = numbers.Where(num => num % 2 == 0).OrderBy(n => n);

Demo

Q & A

?

What’s next?

• 6.12. – Programiranje i testiranje softverskog proizvoda, Denis Sušac (Mono)– Radionica: Odabir tehnologija

• 10.12. – WCF servisi, REST servisi, Načini povezivanja i komunikacije klijenta i servisa, Leo Tot (MSP)

Thank you!ivan.markovic@studentpartner.com