Presented by,

MySQL & O’Reilly Media, Inc.

MySQL, LINQ and theADO.NET Entity Framework

Reggie Burnett, MySQL

David Sceppa, Microsoft

Agenda

From DataSets to data access layers Introducing LINQ Using LINQ to access your data The ADO.NET Entity Framework Introducing ADO.NET Data Services Summary

Working with DataSets

Basic example//Execute a query, retrieve and store the resultsconnectionString = "Data Source=localhost;User ID=...;";commandText = "SELECT CompanyName, City FROM Customers " + "WHERE Country = ?Country";adapter = new MySqlDataAdapter(commandText, connectionString);adapter.SelectCommand.Parameters.AddWithValue("?Country", "Brazil");table = new DataTable();adapter.Fill(table);

//Display the resultsDataGridView resultsGrid = new DataGridView();resultsGrid.DataSource = table;

//Submit pending changescommandBuilder = new MySqlCommandBuilder(adapter);adapter.Update(table);

Working with DataSets

Benefit• Rapid development - Designers, wizards,

bound controls make it easy to write code and generate user interface

Drawbacks• Developers must become SQL experts to

build advanced queries• Code becomes more complex when app

model and database schema diverge

Moving to data access layers

Focus on your application model• Queries expressed in terms of app model• Classes track their own changes

Data access layer responsible for• Translating into SQL queries• Returning results as objects• Submitting pending changes

Moving to data access layers

Basic example//Partial class to separate data access codepublic class Customer {

//Add methods to return data public static List<Customer> GetCustomers(string country) { List<Customer> results = new List<Customer> (); MySqlConnection connection = new MySqlConnection(connectString); connection.Open(); MySqlCommand command = new MySqlCommand(queryString, connection); command.Parameters.AddWithValue("?Country", country); MySqlDataReader reader = command.ExecuteReader(); while (reader.Read()) results.Add(Customer.CreateFromReader(reader)); return results; }

//Support tracking and submitting changes private string origCustomerId, origCompanyName, ...; public void SubmitChanges() { ... }}

Moving to data access layers

Benefit• Division of labor - Manage data access code

separately, only subset of developers need to become SQL gurus

Drawbacks• Data access code quickly gets complex

Classes that span multiple tables Handling inheritance hierarchies Note: Patterns and frameworks emerge

Introducing LINQ

What is LINQ?• Stands for Language INtegrated Query• Allows developers to query data structures

using SQL-like syntax from within their application’s code

• Is available to both C# and Visual Basic developers in Visual Studio 2008

Introducing LINQ

LINQ Example - Querying an array//Create an array of integersint[] myarray = new int[] { 49, 28, 20, 15, 25, 23, 24, 10, 7, 34 };

//Create a query for odd numbersvar oddNumbers = from i in myarray where i % 2 == 1 select i;

//Display the results of the queryforeach (int i in oddNumbers) Console.WriteLine(i);

//Create a query for odd numbers, sortedvar oddNumbers = from i in myarray where i % 2 == 1 orderby i select i;

//Create a query for odd numbers, sorted in descending ordervar oddNumbers = from i in myarray where i % 2 == 1 orderby i descending select i;

//Create a query for odd numbersvar oddNumbers = from i in myarray where i % 2 == 1 select i;

//Compose the original query to create a query for odd numbersvar sorted = from i in oddNumbers orderby i descending select i;

LINQ-enabled classes

Collection classes extended• Arrays, Hashtable, List<T>, etc. LINQ to DataSet• Extended for untyped and strongly typed LINQ to XML Data access technologies• LINQ to SQL• LINQ to Entities

Agenda

From DataSets to data access layers Introducing LINQ Using LINQ to access your data The ADO.NET Entity Framework Introducing ADO.NET Data Services Summary

LINQ to DataSet

DataSet class enhanced to support LINQ• Available via typed and untyped DataSet

Dim ordersQuery = From o In dataSet.Orders _ Where o.CustomerID = "ALFKI" _ Select o

For Each o As NorthwindDataSet.OrdersRow In ordersQuery Console.WriteLine("{0} {1,10:d}", _ o.OrderID, o.OrderDate) Next o

LINQ to DataSet

Benefits• Quickest way to use LINQ w/ .NET 2.0

feature set• Supports query capabilities previously

unavailable using a DataSet• Returns results as series of DataRows or as

anonymous types Limitations

• All client-side processing

Benefits• Rapid application development scenarios• Query processing performed at the server• Designer makes mapping classes to tables

simple Limitations

• Supports limited mapping scenarios• No provider model for extensibilityNo provider model for extensibility

LINQ to SQL

Benefits• Rapid application development scenarios• Query processing performed at the server• Designer makes mapping classes to tables

simple Limitations

• Supports limited mapping scenarios

Agenda

From DataSets to data access layers Introducing LINQ Using LINQ to access your data The ADO.NET Entity Framework Introducing ADO.NET Data Services Summary

What is LINQ to Entities?• LINQ implementation of the Entity Data Model

What is the Entity Data Model?• Definition for your application model• Map between app model, database schema• Advanced mapping scenarios supported One entity mapped across multiple tables Multiple inheritance hierarchy mappings Many-to-many without "link" table in model

What is LINQ to Entities?• LINQ implementation of the Entity Data Model

LINQ to Entities

LINQ to DataSet

DataSet class enhanced to support LINQ• Available via typed and untyped DataSet

Dim ordersQuery = From o In dataSet.Orders _ Where o.CustomerID = "ALFKI" _ Select o

For Each o As NorthwindDataSet.OrdersRow In ordersQuery Console.WriteLine("{0} {1,10:d}", _ o.OrderID, o.OrderDate) Next o

LINQ to Entities or LINQ to SQL? LINQ to SQL

• Shipped with Visual Studio 2008 and .NET 3.5

• Emphasis on rapid application development

• Supports Microsoft SQL Server family of databases

LINQ to Entities• Will ship as an update to .NET 3.5

• Offers a provider model for third-party databases

• Designed for enterprise-grade data scenarios

• Higher level of abstraction for programming databases

• Just one layer of the overall ADO.NET Entity Framework

LINQ to Entities: Generating Queries

Converting LINQ queries to SQL• Compiler converts code into a LINQ expression tree• LINQ to Entities converts LINQ expression tree into

a DbCommandTree based on mapping information DbCommandTree expressed in terms of the

database schema• ADO.NET provider generates a DbCommand• LINQ to Entities executes the DbCommand,

assembles results into the structure(s) specified in the LINQ query

Agenda

From DataSets to data access layers Introducing LINQ Using LINQ to access your data The ADO.NET Entity Framework Introducing ADO.NET Data Services Summary

Entity Framework: LINQ and more

ADO.NET Entity Framework Layers• First implementation of

Entity Data Model (EDM)

• Includes a text-based queryquery language (Entity SQL)

• New Provider – EntityClient

• New ORM stack (Object Services) leverages Entity Client

• LINQ support over Entities

• An evolution of ADO.NET preserving customer investment

ADO.NET ProviderADO.NET Provider

EntityClientEntityClient

ObjectServicesObjectServices

LINQ to EntitiesLINQ to Entities

Entity Framework Query Options

LINQ to Entities

Sweet spot:• Strongly typed queries and results Compile-time type checking and Intellisense

• Results returned as objects: entities / projections• Queries must be well defined at compile time

var ordersQuery = from o in context.Orders where o.Customers.CustomerID == "ALFKI" select o;

foreach (var o in ordersQuery) Console.WriteLine("{0} {1:d}", o.OrderID, o.OrderDate);

Entity Framework Query Options

ObjectQuery<T> / ObjectQuery(Of T)

Sweet spot:• Strongly typed results, text-based queries• Results returned as objects: entities / projections• Queries more loosely defined at compile-time

Dim eql As String = "SELECT VALUE o FROM Orders AS o " & _ " WHERE o.Customer.CustomerID = 'ALFKI'"Dim ordersQuery = context.CreateQuery(Of Order)(esql)

For Each o As Order In ordersQuery Console.WriteLine("{0} {1,10:d} ", o.OrderID, o.OrderDate)Next o

Entity Framework Query Options

EntityClient Provider

Sweet spot:• Untyped queries and results• Results returned as DataReaders• Queries can be generated purely at run time No application model classes needed at compile time

string eSql = "SELECT VALUE o FROM NorthwindEntities.Orders AS o " + "WHERE o.Customers.CustomerID = 'ALFKI'";EntityCommand cmd = new EntityCommand(eSql, connectionString);EntityDataReader rdr = cmd.ExecuteReader();while (rdr.Read()) Console.WriteLine("{0} {1:d}", rdr["OrderID"], rdr["OrderDate"]);

Agenda

From DataSets to data access layers Introducing LINQ Using LINQ to access your data The ADO.NET Entity Framework Introducing ADO.NET Data Services Summary

ADO.NET Data Services

Formerly known as "Project Astoria"• Part of ASP.NET Extensions Preview• Integrated into .NET Framework going forward

Targeting Web development technologies• Silverlight and AJAX• Data returned via Web-friendly formats ATOM (XML-based) and JSON

ADO.NET Data Services

Service exposed via lightweight data access API• Supply both location and query as a URI: http://myserver/data.svc/Customers[ALFKI]/Orders

• Query converted to LINQ inside of service• Supports submitting changes Specialized Entity Framework logic for submitting changes

Online data hosting service available For more information:• http://astoria.mslivelabs.com

Agenda

From DataSets to data access layers Introducing LINQ Using LINQ to access your data The ADO.NET Entity Framework Introducing ADO.NET Data Services Summary

Summary - LINQ

Represents a revolution for developers• Query your objects using SQL-like syntax• LINQ to DataSet Rich query scenarios for data residing in a DataSet

• LINQ to Entities Provider model for working with other data stores Supports enterprise mapping scenarios

Summary - ADO.NET Entity Framework

More than just LINQ to Entities• Also supports text-based query language – ESQL• ObjectQuery<T> for strongly typed results• EntityClient for reader-based results

Enterprise-grade data scenarios Provider model for working with other data stores

Summary - ADO.NET Data Services

Designed for Silverlight, AJAX environments Lightweight API, connect and query via URI Retrieve results via familiar formats• ATOM• JSON

Questions?