The document discusses Entity Framework, an ORM tool from Microsoft. It provides an agenda that will cover what Entity Framework is, how to create an entity model, how to query the model using LINQ and Entity SQL, examples of insert, update and delete operations, and benefits and drawbacks of Entity Framework. Key topics include mapping objects to a relational database, generating entity classes from an existing database, and performing CRUD operations through LINQ queries or Entity SQL.

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Entity Framework

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• What is Entity Framework
• Creating Entity Model
• Querying the Model
• Examples – Insert, Update, Delete
• Benefits
• Drawbacks
❖ Agenda for today

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❖ ORM’s provides a way to map
ORM is:
• (Wikipedia) A programming(Wikipedia) A programming
technique for converting data between incompatible type
systems(Wikipedia) A programming technique for converting
data between incompatible type systems (such as DBMS) in
relational databases(Wikipedia) A programming technique for
converting data between incompatible type systems (such as
DBMS) in relational databases and object-oriented programming
languages.
•It does the plumbing work for you to aggregate, modify
and save your data back to its storage in Object Oriented
manner (easy to understand, maintain and extend)

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❖ What is Entity Framework
• Microsoft’s newest data access technology
• Visual Studio:
– Examines database
– Creates objects that represent data schema
• LINQ (Language Integrated Query)
– Replaces SQL
– Select, sort, filter, etc.

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❖ Creating Entity Model, step 1
• Create a class library project
• Add new item, select the ADO.NET Entity Data Model
template

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❖ Creating Entity Model, step 2

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❖ Creating Entity Model, step 3
• Adjust the entities, mapping etc.

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❖ Querying the Model
• You can query the model in different ways:
– Using LINQ
– Using Entity SQL with Object Services

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❖ Querying the Model
1.Querying with LINQ
var context = new NWEntities();
var query = from c in context.Customers
select c;
foreach(Customer c in query)
Console.WriteLine(c.CompanyName);

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❖ Querying the Model
2. Entity SQL with Object Services
List<Customer> customers =
Context.Customer.ToList();
foreach (Customer c in customers)
Console.WriteLine(c.CompanyName);

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❖ Examples
• INSERT
Console.WriteLine("Create new order");
var order = new Order { CustomerID = "SEVES",
EmployeeID = 1 };
context.AddToOrders(order);
context.SaveChanges();

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❖ Examples
• Update
Console.WriteLine("Changing order");
var order = from o in context.Orders
where o.OrderID == 11078
select o;
order.Single().OrderDate = DateTime.Now;
context.SaveChanges();

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❖ Examples
• Delete
Console.WriteLine("Deleting order");
var order = from o in context.Orders
where o.OrderID == 11078
select o;
context.DeleteObject(order.Single());
context.SaveChanges();

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❖ Benefits
• Eliminates disconnect between code & database
– No sql statements in code
• Use intellisense to write query
• Automatic table joins
• Full CRUD(create retrieve update delete) functionality
• LINQ works on all data collections
– Arrays, lists, dataviews, etc.

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❖ Drawbacks
• Microsoft proprietary technology
• LINQ query syntax different than SQL
• Synchronization between database and entity objects
– Change database
– Rebuild entity objects