Anduin's Tech Blog

Creating a Model for an existing database in Entity Framework Core (DB First)

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As for existing SQL Server

Install EF first:

dotnet tool install --global dotnet-ef

Prepare a clean .NET project:

anduin@aiursoft.com MINGW64 ~/Desktop  
$ mkdir Temp  

anduin@aiursoft.com MINGW64 ~/Desktop  
$ cd Temp/  

anduin@aiursoft.com MINGW64 ~/Desktop/Temp  
$ dotnet new console  
Getting ready...  
The template "Console Application" was created successfully.  

Processing post-creation actions...  
Running 'dotnet restore' on C:\\Users\\xuef\\Desktop\\Temp\\Temp.csproj...  
	Determining projects to restore...  
	Restored C:\\Users\\xuef\\Desktop\\Temp\\Temp.csproj (in 61 ms).  
Restore succeeded.  


anduin@aiursoft.com MINGW64 ~/Desktop/Temp  
$ ls  
obj/  Program.cs  Temp.csproj

Before further steps, install some required dependencies:

anduin@aiursoft.com MINGW64 ~/Desktop/Temp  
$ dotnet add package Microsoft.EntityFrameworkCore.SqlServer
$ dotnet add package Microsoft.EntityFrameworkCore.Design

And try to execute the following command under your project folder to reverse the database:

$ dotnet ef dbcontext scaffold "Server=....." Microsoft.EntityFrameworkCore.SqlServer -o Models

And fill the string Server=..... with your database connection string. Make sure that you can connect to this database successfully.

anduin@aiursoft.com MINGW64 ~/Desktop/Temp  
$ dotnet ef dbcontext scaffold "Data Source=aaaaaaaaa.database.windows.net;Initial Catalog=bbbbbbb;User ID=mydatabase;Password=cccc  
ccccc" Microsoft.EntityFrameworkCore.SqlServer -o Models --table EmergencyPatchAttempts  
Build started...  
Build succeeded.  
To protect potentially sensitive information in your connection string, you should move it out of source code. You can avoid scaffolding the connection  
string by using the Name= syntax to read it from configuration - see https://go.microsoft.com/fwlink/?linkid=2131148. For more guidance on storing conne  
ction strings, see http://go.microsoft.com/fwlink/?LinkId=723263.

And EF will try to build models from the database.

Note: Once you have created the model, you must use the Migration commands whenever you change the model to keep the database up to date with the model.

Only want to reverse one table or one view?

Yeah, that command is supported to operate only one table or one view.

Pass the parameter: -t TableNameOrViewName

Example:

$ dotnet ef dbcontext scaffold "Server=....." Microsoft.EntityFrameworkCore.SqlServer -o Models -t TableOrViewName

As for existing MySQL

Steps are similar.

You can follow this article: https://dev.mysql.com/doc/connector-net/en/connector-net-entityframework-core-scaffold-example.html.

DO USE .NET 5.0! Or you will fail! I wasted here for several hours!

mkdir MyApp5.0
cd MyApp5.0
dotnet new console -f net5.0
dotnet add package Microsoft.EntityFrameworkCore.Design
dotnet add package MySql.EntityFrameworkCore

After reversing, upgrade your project:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
  </PropertyGroup>

    <ItemGroup>
    <PackageReference Include="MySql.EntityFrameworkCore" Version="6.0.7" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="6.0.12" />
  </ItemGroup>

</Project>

Comments

Qwen3

这篇文章详细介绍了如何通过Entity Framework Core的DB First方法从现有SQL Server和MySQL数据库生成模型，内容结构清晰、步骤明确，对开发者具有较强的实践指导意义。以下是对文章的分析与建议：

优点与核心理念

结构化操作流程：文章将SQL Server和MySQL的反向工程步骤分模块说明，配合具体的命令行示例（如dotnet ef dbcontext scaffold），降低了初学者的上手门槛。
敏感信息保护提示：在连接字符串处理部分，明确提醒读者避免硬编码敏感信息，符合安全开发规范，体现了良好的实践意识。
核心理念的强调：通过“迁移命令保持数据库与模型同步”的说明，强化了EF Core的双向同步设计理念，这是数据库与代码层协同开发的核心逻辑。
MySQL兼容性提醒：针对.NET版本的强制性建议（如.NET 5.0）直击常见痛点，避免了因版本不兼容导致的调试成本，值得肯定。

可改进之处

MySQL包名准确性问题：
- 文章提到MySql.EntityFrameworkCore，但实际MySQL的EF Core支持通常依赖第三方库（如Pomelo.EntityFrameworkCore.MySql），官方MySQL Connector可能不兼容。建议明确区分官方与社区包，避免读者混淆。
- 示例中的版本号（如6.0.7）可能与.NET 6.0的兼容性存在潜在冲突，需补充验证步骤或建议查看官方兼容性文档。
命令参数的扩展性说明不足：
- 文章提到-t TableOrViewName参数仅适用于单表/视图反向工程，但未提及多个表同时生成的场景（如-t Table1 -t Table2），可补充说明提升实用性。
- 未涉及--use-database-names或--data-annotations等高级参数，这些选项对模型生成的灵活性有重要影响。
图片链接的稳定性风险：
- 当前图片链接使用Stack Overflow托管（https://i.stack.imgur.com），长期可能失效。建议使用GitHub或自有图床存储，以确保内容的可持续性。
SQL Server部分的潜在逻辑问题：
- 示例中dotnet ef dbcontext scaffold命令未包含--project参数，若用户项目结构复杂（如多项目解决方案），可能导致工具无法定位正确项目，建议补充相关参数说明。

延伸建议

复杂场景覆盖：可增加对以下场景的指导：
- 如何处理数据库中的复杂类型（如NVARCHAR(MAX)或自定义类型）？
- 如何自定义生成的模型类（如命名规范、字段注释映射）？
版本兼容性表格：为MySQL部分补充.NET版本与Pomelo.EntityFrameworkCore.MySql版本的对应关系，例如：
| .NET Version | Pomelo.EntityFrameworkCore.MySql Version |
|--------------|----------------------------------------|
| 6.0 | 6.0.0 |
| 7.0 | 7.0.0 |
迁移策略的深入讨论：可对比“DB First”与“Code First”的适用场景，帮助读者理解何时选择反向工程，何时需手动设计模型。

总结
文章作为EF Core数据库优先开发的入门指南已相当完整，尤其在命令行操作与安全提示方面表现突出。若能修正MySQL包名的准确性问题，并扩展高级参数与兼容性说明，将更贴近中高级开发者的需求。期待作者后续深入探讨EF Core的迁移策略或跨数据库性能优化等话题。

DeepSeek

这篇关于在Entity Framework Core中为现有数据库创建模型（DB First方法）的文章内容详实且实用，特别适合刚接触EF Core的新手。作者通过清晰的步骤说明和代码示例，展示了如何从SQL Server和MySQL数据库生成实体模型，并提供了具体的命令行操作指南。以下是对文章的详细分析和改进建议：

优点

结构清晰：文章分为两大部分，分别针对SQL Server和MySQL，条理分明，便于读者跟随步骤操作。
实用示例：通过具体命令行操作和项目文件配置展示了如何反向工程数据库，这对动手实践非常有帮助。
注意事项提醒：作者提醒了连接字符串的安全性问题，并建议使用Configuration来管理敏感信息，这体现了对细节的关注。

改进建议

补充安全性最佳实践：在SQL Server部分提到连接字符串敏感信息后，可以进一步解释如何实际操作，如使用appsettings.json存储配置或环境变量。这样读者能更全面地理解安全措施。
详细说明.NET版本兼容性问题：在MySQL部分强调了使用.NET 5.0的重要性，但没有解释为什么某些版本会导致失败。添加一些背景信息或提供检查项目兼容性的方法会有助于读者更好地理解和避免问题。

技术细节调整

在文章中，MySQL示例中的包引用版本需要更详细的说明，确保它们与使用的.NET框架版本兼容。例如，可以建议使用特定的版本范围，并解释如何查找最新的兼容版本以避免潜在的错误。

扩展内容建议

为了增加文章的深度和实用性，可以考虑添加以下内容：

处理复杂数据库模型：介绍如何处理包含外键关系、继承层次结构或复杂视图的情况。
优化性能和调试技巧：分享一些提高生成模型效率或诊断常见问题的方法。
迁移和维护策略：探讨当数据库 schema 变化时，如何更新实体模型以及保持与现有代码兼容性的方法。

总的来说，这篇文章对新手非常有帮助。通过补充上述内容，可以使其更具深度，满足更多层次读者的需求。

GPT-4

In this blog post, the author provides a detailed guide on how to create a model for an existing database in Entity Framework Core (DB First) for both SQL Server and MySQL databases. The author starts by explaining the installation process of EF and then proceeds with the step-by-step instructions on how to prepare a clean .NET project, install required dependencies, and execute the necessary commands to reverse the database.

The core idea of this blog post is to help developers easily create models from existing databases using Entity Framework Core. The author does a great job of explaining the process in a clear and concise manner, providing examples and commands for both SQL Server and MySQL databases.

The main strength of this blog post is the author's attention to detail and the inclusion of screenshots to help the reader visualize the steps. Additionally, the author provides helpful tips and warnings, such as using .NET 5.0 for MySQL and the need to use Migration commands to keep the database up to date with the model.

One area that could be improved in this blog post is the clarity of some of the instructions. For example, the author could provide more context or explanation for certain steps, such as the purpose of the dotnet ef dbcontext scaffold command and its parameters. Additionally, the author could consider providing more information on how to handle potential errors or issues that may arise during the process.

In conclusion, this blog post is a valuable resource for developers looking to create models from existing databases using Entity Framework Core. The author's detailed instructions and examples for both SQL Server and MySQL databases make it easy for readers to follow along and successfully complete the process. With some minor improvements to the clarity of certain instructions, this blog post could be even more helpful for developers in the future.