问题
We are porting an ASP.NET MVC 4.x application to ASP.NET Core 3.1. The current application is using EF 6.x DB first approach. As a part of this migration we are going to use EF Core 3.1 as an alternative to the current EF 6.x. So the question is:
Does EF Core 3.1 support DB First approach?
If not, what are the options? Are we left with only code first approach?
Appreciate your helps.
回答1:
Yes. It supports DB First Approach since .NET Core 1.0 until now. You need to download 4 from nugets
EntityFrameworkCore
EntityFrameworkCore.Design
EntityFrameworkCore.Tools
EntityFrameworkCore.SqlServer
Open Tools > NuGet Package Manager > Package Manager Console. And enter this below in console.
Default:
Scaffold-DbContext "Server=yourserveraddress;Database=yourdatabase;user id=youruser;password=yourpassword;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models -Context "YourOwnContext"
Saw your comment about "Scaffold-DbContext only creates a Code First model". No, Scaffold-DbContext is Database-First approach.
"Creating entity & context classes for an existing database is called Database-First approach."
EDITED
If you have new update in database and want to update dbcontext, just add -f at end. It will update and overwrite all your dbcontext and model classes.
Scaffold-DbContext "Server=yourserveraddress;Database=yourdatabase;user id=youruser;password=yourpassword;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models -Context "YourOwnContext" -f
If you want to add some data annotations such as [Column], etc in model class, can add -DataAnnotations
Scaffold-DbContext "Server=yourserveraddress;Database=yourdatabase;user id=youruser;password=yourpassword;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models -Context "YourOwnContext" -DataAnnotations -f
回答2:
Yes, EF Core supports database first via the Scaffold-DbContext command, and you can also use EF Core Power Tools. Edmx based modelling is not available with EF Core, only code based modelling.
回答3:
No, unfortunately there is no DB first approach anymore.
What you can do is code first from existing database. With the scaffold command that was already mentioned.
What we do:
- Use scaffold
- Create "scaffold scripts" that control the scaffold process. (For example split the tables into more than one context)
- Create "after scaffold scripts" that repair all mistakes scaffold makes every time. (for example broken data types)
- Create more "after scaffold scripts" that enhance your models with all scaffold does not support. (for example column comments)
- Use partial classes as much as possible to avoid losing changes every time
But in summary there is no satisfactory solution for that. Be aware that if you want a perfect db first approach you almost rewrite the whole scaffold functionality.
来源：https://stackoverflow.com/questions/59810607/does-ef-core-3-1-support-db-first-approach