比较 EF Core 和 EF6Compare EF Core & EF6
Entity Framework 是适用于.NET 的对象关系映射程序 (O/RM)。Entity Framework is an object-relational mapper (O/RM) for .NET. 本文比较了两个版本：Entity Framework 6 和 Entity Framework Core。This article compares the two versions: Entity Framework 6 and Entity Framework Core.
Entity Framework 6Entity Framework 6
Entity Framework 6 (EF6) 是一种久经验证的数据访问技术。Entity Framework 6 (EF6) is a tried and tested data access technology. 2008 年，它作为 .NET Framework 3.5 SP1 和 Visual Studio 2008 SP1 的一部分首次发布。It was first released in 2008, as part of .NET Framework 3.5 SP1 and Visual Studio 2008 SP1. 从 4.1 版开始，已作为 EntityFramework NuGet 包发布。Starting with the 4.1 release it has shipped as the EntityFramework NuGet package. 从 3.0 版开始，EF6 在 .NET Framework 4.x 和 .NET Core 上运行。EF6 runs on the .NET Framework 4.x and .NET Core from 3.0 onwards.
EF6 产品仍受支持，并将继续提供 bug 修复和细微改进。EF6 continues to be a supported product, and will continue to see bug fixes and minor improvements.
Entity Framework CoreEntity Framework Core
Entity Framework Core (EF Core) 是在 2016 年首次发布的 EF6 的完全重写。Entity Framework Core (EF Core) is a complete rewrite of EF6 that was first released in 2016. 它附带于 Nuget 包中，是 Microsoft.EntityFrameworkCore 的主要组成部分。It ships in Nuget packages, the main one being Microsoft.EntityFrameworkCore. EF Core 是一款跨平台产品，可以在 .NET Core 上运行。EF Core is a cross-platform product that runs on .NET Core.
EF Core 旨在提供类似于 EF6 的开发人员体验。EF Core was designed to provide a developer experience similar to EF6. 大多数顶级 API 保持不变，因此，用过 EF6 的开发人员都会对 EF Core 感到很熟悉。Most of the top-level APIs remain the same, so EF Core will feel familiar to developers who have used EF6.
功能比较Feature comparison
EF Core 提供了在 EF6 中不会实现的新功能（如备选键、批量更新以及 LINQ 查询中的混合客户端/数据库评估。EF Core offers new features that won't be implemented in EF6 (such as alternate keys, batch updates, and mixed client/database evaluation in LINQ queries. 但由于它是一个新代码库，所以会缺少一些 EF6 中的功能。But because it's a new code base, it also lacks some features that EF6 has.
下表比较了 EF Core 和 EF6 中可用的功能。The following tables compare the features available in EF Core and EF6. 这只是大致比较，没有列出全部功能或解释不同 EF 版本中相同功能之间的差异。It's a high-level comparison and doesn't list every feature or explain differences between the same feature in different EF versions.
EF Core 列指出了功能首次出现的产品版本。The EF Core column indicates the product version in which the feature first appeared.
创建模型Creating a model
| 功能Feature | EF 6 EF 6 | EF CoreEF Core |
|---|---|---|
| 基本类映射Basic class mapping | 是Yes | 1.01.0 |
| 带有参数的构造函数Constructors with parameters | 2.12.1 | |
| 属性值转换Property value conversions | 2.12.1 | |
| 没有键的映射类型Mapped types with no keys | 2.12.1 | |
| 约定Conventions | 是Yes | 1.01.0 |
| 自定义约定Custom conventions | 是Yes | 1.0（部分）1.0 (partial) |
| 数据注释Data annotations | 是Yes | 1.01.0 |
| Fluent APIFluent API | 是Yes | 1.01.0 |
| 继承：每个层次结构一个表 (TPH)Inheritance: Table per hierarchy (TPH) | 是Yes | 1.01.0 |
| 继承：每个类型一个表 (TPT)Inheritance: Table per type (TPT) | 是Yes | |
| 继承：每个具体类一个表 (TPC)Inheritance: Table per concrete class (TPC) | 是Yes | |
| 阴影状态属性Shadow state properties | 1.01.0 | |
| 备用键Alternate keys | 1.01.0 | |
| 多对多，无联接实体Many-to-many without join entity | 是Yes | |
| 密钥生成：数据库Key generation: Database | 是Yes | 1.01.0 |
| 密钥生成：客户端Key generation: Client | 1.01.0 | |
| 复杂/已拥有类型Complex/owned types | 是Yes | 2.02.0 |
| 空间数据Spatial data | 是Yes | 2.22.2 |
| 模型的图形可视化效果Graphical visualization of model | 是Yes | |
| 图形模型编辑器Graphical model editor | 是Yes | |
| 模型格式：代码Model format: Code | 是Yes | 1.01.0 |
| 模型格式：EDMX (XML)Model format: EDMX (XML) | 是Yes | |
| 从数据库更新模型：命令行Create model from database: Command line | 是Yes | 1.01.0 |
| 从数据库更新模型：VS 向导Create model from database: VS wizard | 是Yes | |
| 从数据库更新模型Update model from database | 部分Partial | |
| 全局查询筛选器Global query filters | 2.02.0 | |
| 表拆分Table splitting | 是Yes | 2.02.0 |
| 实体拆分Entity splitting | 是Yes | |
| 数据库标量函数映射Database scalar function mapping | 差Poor | 2.02.0 |
| 字段映射Field mapping | 1.11.1 | |
| 可为空引用类型 (C# 8.0)Nullable reference types (C# 8.0) | 3.03.0 |
查询数据Querying data
| 功能Feature | EF6 EF6 | EF CoreEF Core |
|---|---|---|
| LINQ 查询LINQ queries | 是Yes | 1.0（进行中，针对复杂查询）1.0 (in-progress for complex queries) |
| 可读内容生成的 SQLReadable generated SQL | 差Poor | 1.01.0 |
| GroupBy 转换GroupBy translation | 是Yes | 2.12.1 |
| 加载关联数据：预先Loading related data: Eager | 是Yes | 1.01.0 |
| 加载关联数据：预先加载派生类型Loading related data: Eager loading for derived types | 2.12.1 | |
| 加载关联数据：延迟Loading related data: Lazy | 是Yes | 2.12.1 |
| 加载关联数据：ExplicitLoading related data: Explicit | 是Yes | 1.11.1 |
| 原生 SQL 查询：实体类型Raw SQL queries: Entity types | 是Yes | 1.01.0 |
| 原生 SQL 查询：无键实体类型Raw SQL queries: Keyless entity types | 是Yes | 2.12.1 |
| 原生 SQL 查询：使用 LINQ 编写Raw SQL queries: Composing with LINQ | 1.01.0 | |
| 显式编译的查询Explicitly compiled queries | 差Poor | 2.02.0 |
| 基于文本的查询语言（实体 SQL）Text-based query language (Entity SQL) | 是Yes | |
| await foreach (C# 8.0)await foreach (C# 8.0) | 3.03.0 |
保存数据Saving data
| 功能Feature | EF6 EF6 | EF CoreEF Core |
|---|---|---|
| 更改跟踪：快照Change tracking: Snapshot | 是Yes | 1.01.0 |
| 更改跟踪：通知Change tracking: Notification | 是Yes | 1.01.0 |
| 更改跟踪：代理Change tracking: Proxies | 是Yes | |
| 访问跟踪的状态Accessing tracked state | 是Yes | 1.01.0 |
| 开放式并发Optimistic concurrency | 是Yes | 1.01.0 |
| 事务Transactions | 是Yes | 1.01.0 |
| 批处理语句Batching of statements | 1.01.0 | |
| 存储过程映射Stored procedure mapping | 是Yes | |
| 断开连接低级别 API 图形Disconnected graph low-level APIs | 差Poor | 1.01.0 |
| 断开连接端到端图形Disconnected graph End-to-end | 1.0（部分）1.0 (partial) |
其他功能Other features
| 功能Feature | EF6 EF6 | EF CoreEF Core |
|---|---|---|
| 迁移Migrations | 是Yes | 1.01.0 |
| 数据库创建/删除 APIDatabase creation/deletion APIs | 是Yes | 1.01.0 |
| 种子数据Seed data | 是Yes | 2.12.1 |
| 连接复原Connection resiliency | 是Yes | 1.11.1 |
| 生命周期挂钩（事件、截取）Lifecycle hooks (events, interception) | 是Yes | |
| 简单的日志记录 (Database.Log)Simple Logging (Database.Log) | 是Yes | |
| DbContext 池DbContext pooling | 2.02.0 |
数据库提供程序Database providers
| 功能Feature | EF6 EF6 | EF CoreEF Core |
|---|---|---|
| SQL ServerSQL Server | 是Yes | 1.01.0 |
| MySQLMySQL | 是Yes | 1.01.0 |
| postgresqlPostgreSQL | 是Yes | 1.01.0 |
| OracleOracle | 是Yes | 1.01.0 |
| SQLiteSQLite | 是Yes | 1.01.0 |
| SQL Server CompactSQL Server Compact | 是Yes | 1.0 (1)1.0 (1) |
| DB2DB2 | 是Yes | 1.01.0 |
| FirebirdFirebird | 是Yes | 2.02.0 |
| Jet (Microsoft Access)Jet (Microsoft Access) | 2.0 (1)2.0 (1) | |
| Cosmos DBCosmos DB | 3.03.0 | |
| 内存中（用于测试）In-memory (for testing) | 1.01.0 |
1 SQL Server Compact 和 Jet 提供程序仅适用于 .NET Framework（而不适用于 .NET Core）。1 The SQL Server Compact and Jet providers only work on .NET Framework (not on .NET Core).
.NET 实现.NET implementations
| 功能Feature | EF6 EF6 | EF CoreEF Core |
|---|---|---|
| .NET Framework.NET Framework | 是Yes | 1.0（在 3.0 中删除）1.0 (removed in 3.0) |
| .NET Core.NET Core | 是（在 6.3 中添加）Yes (added in 6.3) | 1.01.0 |
| Mono 和 XamarinMono & Xamarin | 1.0（进行中）1.0 (in-progress) | |
| UWPUWP | 1.0（进行中）1.0 (in-progress) |
针对新应用程序的选择指南Guidance for new applications
如果以下两个条件都成立，请考虑为新应用程序使用 EF Core：Consider using EF Core for a new application if both of the following conditions are true:
- 应用需要.NET Core 的功能。The app needs the capabilities of .NET Core. 有关详细信息，请参阅在 .NET Core 和 .NET Framework 之间进行选择以用于服务器应用。For more information, see Choosing between .NET Core and .NET Framework for server apps.
- EF Core 支持应用需要的所有功能。EF Core supports all of the features that the app requires. 如果缺少所需的功能，请检查 EF Core 路线图，了解是否有计划在将来为其提供支持。If a desired feature is missing, check the EF Core Roadmap to find out if there are plans to support it in the future.
如果以下两个条件都成立，请考虑使用 EF6：Consider using EF6 if both of the following conditions are true:
- 应用将在 Windows 和 .NET Framework 4.0 或更高版本上运行。The app will run on Windows and the .NET Framework 4.0 or later.
- EF6 支持应用需要的所有功能。EF6 supports all of the features that the app requires.
针对现有 EF6 应用程序的选择指南Guidance for existing EF6 applications
由于 EF Core 有一些根本性变化，我们不建议将 EF6 应用程序迁移至 EF Core，除非有令人信服的理由进行此项更改。Because of the fundamental changes in EF Core, we do not recommend moving an EF6 application to EF Core unless there is a compelling reason to make the change. 如果想迁移到 EF Core 以使用新功能，请确保你了解其各项限制。If you want to move to EF Core to use new features, make sure you're aware of its limitations. 有关详细信息，请参阅从 EF6 到 EF Core 的迁移。For more information, see Porting from EF6 to EF Core. 从 EF6 到 EF Core 更像是迁移而不是升级。The move from EF6 to EF Core is more a port than an upgrade.
后续步骤Next steps
有关详细信息，请参阅文档：For more information, see the documentation:
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