深入实践Entity Framework Core 2nd版

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"Entity Framework Core in Action 2nd Edition 是一本深入探讨 Entity Framework Core 的书籍，由 JonPSmith 撰写，Julie Lerman 撰写前言。本书覆盖了从设置 EF Core 到性能优化的广泛主题，旨在帮助开发者全面掌握这一流行的 ORM 工具在实际项目中的应用。" 本书主要涵盖了以下知识点： 1. **设置 EF Core**：在第 1、2 和 7 章中介绍，包括如何安装、配置和初始化 Entity Framework Core，确保开发环境准备就绪。 2. **查询数据库**：在第 3.1、3.2 和 6.8 至 6.10 章讲解，涵盖了如何使用 LINQ 或原始 SQL 查询数据，以及各种查询操作和技巧。 3. **创建、更新、删除**：在第 1.6、1.8 和 6.8 至 6.10 章讨论，涵盖了如何通过 EF Core 插入、更新和删除数据库记录。 4. **EF Core 内部工作原理**：在第 4.2、4.4 和 5.4 章中探讨，揭示了 EF Core 如何与数据库交互，以及其内部机制。 5. **业务逻辑**：第 5.1 和 5.4 章涉及如何在 EF Core 中实现和管理业务逻辑，以满足应用程序的需求。 6. **ASP.NET Core**：在第 5.2 和 5.3 章中介绍，讲解如何在 ASP.NET Core Web 应用程序中集成和使用 EF Core。 7. **依赖注入**：在第 5.8 和 5.9 章讨论，阐述如何利用 .NET Core 的依赖注入容器来管理 EF Core 的上下文实例。 8. **异步编程**：第 7.1 和 7.2 章讲述了如何在 EF Core 中使用 async/await 进行非阻塞操作，提高应用程序的性能和响应性。 9. **非关系型数据库配置**：在第 8.1 至 8.4 章中介绍，涵盖了如何配置 EF Core 以支持非关系型数据库，如 NoSQL 数据库。 10. **关系配置**：第 8.12 和 8.13 章讲解了如何定义和管理实体之间的关系，如一对一、一对多和多对多关系。 11. **表映射配置**：在第 9.2 至 9.8 章中，详细阐述了如何自定义实体到数据库表的映射，以满足特定需求。 12. **数据库迁移**：第 10.3 至 10.7 及 15.7 章讨论了数据库模型变更时的迁移策略，以保持数据库结构与代码同步。 13. **并发问题处理**：在第 15.3 章中，介绍了如何处理并发冲突，确保数据的一致性和完整性。 14. **使用原始 SQL**：在第 13.3、4.2、13.4 和 13.5 章中，展示了如何在必要时直接执行 SQL 查询，以获得更细粒度的控制。 15. **领域驱动设计（DDD）**：在第 14.1、15.2、15.4、15.9、16.7 和 16.8 章中，介绍了如何结合 EF Core 实现领域驱动设计原则，构建更健壮的系统。 16. **性能调优**：在第 16.1、16.3、16.4 和 17.5 章中，提供了性能优化的策略和最佳实践，以提升 EF Core 应用的运行效率。 17. ** CosmosDB 和其他数据库**：在第 4、7 和 10 章中，讲解了如何使用 EF Core 配合 Azure Cosmos DB 或其他数据库服务。 18. **数据验证**：第 17.2 和 17.3 章介绍了数据验证的机制，确保输入数据的质量。 19. **单元测试**：在附录 A.2 和 A.1 章中，提供了编写和执行针对 EF Core 的单元测试的方法和示例。本书是针对 Entity Framework Core 的综合指南，无论你是初学者还是经验丰富的开发者，都能从中受益，提升在 .NET 开发中的数据库操作技能。

CONTENTS

xiv

340Going deeper into the DbContext

11.1 Overview of the DbContext class’s properties 341

11.2 Understanding how EF Core tracks changes 341

11.3 Looking at commands that change an entity’s State 343

The Add command: Inserting a new row into the database 344

The Remove method: Deleting a row from the database 344

Modifying an entity class by changing the data in that entity

class 345

■

Modifying an entity class by calling the Update

method 346

■

The Attach method: Start tracking an existing

untracked entity class 347

■

Setting the State of an entity

directly 347

■

TrackGraph: Handling disconnected updates

with relationships 348

11.4 SaveChanges and its use of ChangeTracker.DetectChanges 349

How SaveChanges finds all the State changes 350

■

What to do if

ChangeTracker.DetectChanges is taking too long 351

■

Using the

entities’ State within the SaveChanges method 356

■

Catching

entity class’s State changes via events 358

■

Triggering events

when SaveChanges/SaveChangesAsync is called 361

■

EF Core

interceptors 362

11.5 Using SQL commands in an EF Core application 363

FromSqlRaw/FromSqlInterpolated: Using SQL in an EF Core

query 364

■

ExecuteSqlRaw/ExecuteSqlInterpolated: Executing a

nonquery command 365

■

AsSqlQuery Fluent API method:

Mapping entity classes to queries 365

■

Reload: Used after

ExecuteSql commands 367

■

GetDbConnection: Running your

own SQL commands 367

11.6 Accessing information about the entity classes

and database tables 368

Using context.Entry(entity).Metadata to reset primary keys 369

Using context.Model to get database information 371

11.7 Dynamically changing the DbContext’s

connection string 372

11.8 Handling database connection problems 373

Handling database transactions with EF Core’s execution

strategy 374

■

Altering or writing your own execution

strategy 375

CONTENTS

ART

3 .................................................................... 379

Using entity events to so 381lve business problems

12.1 Using events to solve business problems 382

Example of using domain events 382

■

Example of integration

events 383

12.2 Defining where domain events and integration

events are useful 384

12.3 Where might you use events with EF Core? 385

Pro: Follows the SoC design principle 386

■

Pro: Makes

database updates robust 386

■

Con: Makes your application

more complex 387

■

Con: Makes following the flow of the code

more difficult 387

12.4 Implementing a domain event system with EF Core 387

Create some domain events classes to be triggered 388

■

Add code

to the entity classes to hold the domain events 389

■

Alter the entity

class to detect a change to trigger an event on 390

■

Create event

handlers that are matched to the domain events 390

■

Build an

Event Runner that finds and runs the correct event handler 391

Override SaveChanges and insert the Event Runner before

SaveChanges is called 394

■

and all the event handlers 395

12.5 Implementing an integration event system with EF Core 396

Building a service that communicates with the warehouse 398

Overriding SaveChanges to handle the integration event 399

12.6 Improving the domain event and integration event

implementations 400

Generalizing events: Running before, during, and after the call to

SaveChanges 401

■

Adding support for async event handlers 402

Handling multiple event handers for the same event 403

Handling event sagas in which one event kicks off another event 403

Domain-Driven Design and other architectural approaches

405

13.1

A good software architecture

makes it easier to build and

maintain your application

406

13.2

The Book App’s evolving architecture

406

Building a modular monolith to enforce the SoC principles

408

Using DDD principles both architecturally and on the entity

classes

409

■

Applying a clean architecture as described by Robert

C. Martin

410

CONTENTS

xvi

13.3 Introduction to DDD at the entity class level 410

13.4 Altering the Book App entities to follow

the DDD approach 411

Changing the properties in the Book entity to read-only 411

Updating the Book entity properties via methods in the entity

class 413

■

Controlling how the Book entity is created 415

Understanding the differences between an entity and a value

object 416

■

Minimizing the relationships between entity

classes 416

■

Grouping entity classes 417

■

Deciding when

the business logic shouldn’t be run inside an entity 418

Applying DDD’s bounded context to your application’s

DbContext 420

13.5 Using your DDD-styled entity classes in your

application 421

Calling the AddPromotion access method via a repository

pattern 422

■

Calling the AddPromotion access method via

a class-to-method-call library 424

■

Adding a Review to the Book

entity class via a repository pattern 426

■

Adding a Review to the

Book entity class via a class-to-method-call library 427

13.6 The downside of DDD entities: Too many access

methods 428

13.7 Getting around performance issues in DDD-styled

entities 429

Allow database code into your entity classes 430

■

Make the

Review constructor public and write nonentity code to add a

Review 431

■

Use domain events to ask an event handler to add

a review to the database 432

13.8 Three architectural approaches: Did they work? 433

A modular monolith approach that enforces SoC by using projects 433

DDD principles, both architecturally and on the entity classes 434

Clean architecture as described by Robert C. Martin 435

438EF Core performance tuning

14.1 Part 1: Deciding which performance issues to fix 439

“Don’t performance-tune too early” doesn’t mean you stop

thinking

439

■

How do you decide what’s slow and needs

performance tuning?

440

■

The cost of finding and fixing

performance issues

441

14.2

Part 2: Techniques for diagnosing a performance issue

442

Stage 1: Get a good overview, measuring the user’s experience

443

Stage 2: Find all the database code involved in the feature you’re

CONTENTS

xvii

tuning 444

■

Stage 3: Inspect the SQL code to find poor

performance 444

14.3 Part 3: Techniques for fixing performance issues 446

14.4 Using good patterns makes your application

perform well 447

Using Select loading to load only the columns you need 447

Using paging and/or filtering of searches to reduce the rows you

load 448

■

Warning: Lazy loading will affect database

performance 448

■

Always adding the AsNoTracking method to

read-only queries 449

■

Using the async version of EF Core

commands to improve scalability 449

■

Ensuring that your

database access code is isolated/decoupled 449

14.5 Performance antipatterns: Database queries 450

Antipattern: Not minimizing the number of calls to the

database 450

■

Antipattern: Missing indexes from a property

that you want to search on 451

■

Antipattern: Not using the

fastest way to load a single entity 452

■

Antipattern: Allowing

too much of a data query to be moved into the software side 453

Antipattern: Not moving calculations into the database 453

Antipattern: Not replacing suboptimal SQL in a LINQ query 454

Antipattern: Not precompiling frequently used queries 454

14.6 Performance antipatterns: Writes 455

Antipattern: Calling SaveChanges multiple times 456

Antipattern: Making DetectChanges work too hard 457

Antipattern: Not using HashSet<T> for navigational collection

properties 458

■

Antipattern: Using the Update method when you

want to change only part of the entity 458

■

Antipattern: Startup

issue—Using one large DbContext 458

14.7 Performance patterns: Scalability of database

accesses 459

Using pooling to reduce the cost of a new application’s DbContext 460

Adding scalability with little effect on overall speed 460

■

Helping

your database scalability by making your queries simple 461

■

Scaling

up the database server 461

■

Picking the right architecture for

applications that need high scalability 461

Master class on performanc 463e-tuning database queries

15.1 The test setup and a summary of the four performance

approaches 464

15.2 Good LINQ approach: Using an EF Core Select

query 466

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