DAT303 - Entity Framework: Application Patterns Pablo Castro Technical Lead, Microsoft Corporation

Session Prerequisites.NET Framework basics ADO.NET Entity Framework basics In TechEd: DAT201 - Entity Framework Introduction Creation of applications with relational databases

Session Objectives and Agenda Session goal: describe concrete application scenarios for the Entity Framework Brief Introduction to the Entity Framework Starting simple: 2-tier applications Getting real: web applications Getting fancy: n-tier applications and services

The ADO.NET Entity Framework The next layer up in the ADO.NET stack Describe your data using a conceptual model, we’ll do the rest Entity Data Model design tools Declarative mapping to the database Generation of.NET classes for your business entities Query using LINQ and Entity SQL Handle updates automatically, SQL-gen or stored-procedures

2-Tier Applications When? Small applications and tools Trusted clients Application types Windows applications using data-binding Single-task console applications UI and application logic Database server, may include some logic Entity Framework

Aspects to Consider Leveraging features Entity Framework has data-binding support built-in Identity resolution maintains object identity in long-running applications Be careful with… Sharing a single context object makes code simpler… …but you need to recycle it or prune it periodically Stale data in the client, concurrency violations more likely

Web Applications When? Data-driven web applications Database can be used directly by web application Characteristics Most logic runs in web server Entity Framework used in web server UI in web browser Database server Entity Framework UI rendering + business logic

Aspects to Consider Usage patterns Short-lived contexts, create a new one every page hit If absolutely needed, round-trip entities in ASP.NET view state Leveraging features Query results work well with data-aware controls Turn-off object tracking if not going to make changes Query-caching/pre-compilation will speed up execution and lower CPU utilization Web application-friendly connection string syntax Things to avoid Do not store context/connections in application-/session-state

Service/Business Logic Tier Data Tier Consumers/Presentation Tier Service contract Multi-Tier Applications When? Medium to large enterprise applications Characteristics Strong UI/business logic separation Enables service- orientation Enables re-use of services and components UI in web browser Entity Framework Desktop application Web server

Strict Contracts Style Typically SOAP-based web services interface WCF is the best tool for this Client proxies automatically generated for consuming apps Entity types may or may not be appropriate Sometimes it is better to have separate service types State management can be tricky Service calls need to re-build state before calling into the Entity Framework Use ObjectContext.Attach()/.Attach()

Flexible Data Interfaces Style Exposes the data in a more flexible way, at the expense of a less strict contract Use ADO.NET Data Services framework a.k.a. “Project Astoria” Data is exposed over HTTP Each entity becomes a resource URIs are used to point to data (both read and write if enabled) Clients for.NET, Silverlight and Javascript available Or plain HTTP can be used for broader reach

Features to Round it up This sessions discussed patterns, not features Some key features commonly applied to real-world scenarios Flexible mapping capabilities, declarative and query-based Stored-procedures support for data retrieval and update Integration with System.Transactions Provider model for multiple database support Graphical tools for authoring models and mappings

Summary The ADO.NET Entity Framework automatically generates a data-access layer from a conceptual model Each application scenario has its specific requirements, and the Entity Framework provides the building blocks to handle them

Q&A

Related Content Breakout Sessions DAT201 Entity Framework Introduction DAT312 Programming SQL Server 2008 WEB313 Project Astoria: Data Services for the Web TLA308 LINQ to SQL: Accessing Relational Data with Language Integrated Query TLA326 LINQ to Entities – Use LINQ to access ADO.NET Entity Data Models Interactive Sessions DAT01-IS Tell Us Where it Hurts! SQL Server Product Feedback Discussion TLA06-IS LINQ to “X”, ADO.NET Entity Framework, DataSets & Co – What is it with all these Data Access Technologies?

Resources Data Team site in MSDN ADO.NET Team blog My blog

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