关于用DbContextDesignFactory做数据执行迁移命令

[MingHuiJian]

因为我想将Migrations文件放到Infrastructure,所以使用IDesignTimeDbContextFactory接口 在new DbContextOptionsBuilder时因为框架的构造AppDbContextBase构造函数必须要有IMediator，使用数据库迁移命令总是报错 public class ApplicationDbContextDesignFactory : IDesignTimeDbContextFactory { public XxxxDbContextCreateDbContext(string[] args) { IServiceCollection services = new ServiceCollection(); var provider = services.BuildServiceProvider(); services.AddMediatR(cfg => cfg.RegisterServicesFromAssemblies(Assembly.GetExecutingAssembly())); var mediator = provider.GetRequiredService(); return new(new DbContextOptionsBuilder() .UseMySql("Server=****;User ID=mesuser;Password=**;Port=3337;Database=Xxxx;CharSet=UTF8mb4;SslMode=none;AllowPublicKeyRetrieval=true", new MySqlServerVersion(new Version(8, 0, 32))).Options, mediator, provider); } }

Unable to create a 'DbContext' of type ''. The exception 'No service for type 'MediatR.IMediator' has been registered.' was thrown while attempting to create an instance. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728

[witskeeper]

有StackTrace信息吗？

[witskeeper]

XxxxDbContext 的定义是否将参数传给AppDbContextBase

[MingHuiJian]

只是在包管理器执行迁移命令Add-Migration InitialCreate没有StackTrace信息

[MingHuiJian]

XxxxDbContext 将参赛数传给AppDbContextBase了的 public XxxxDbContext (DbContextOptions options, IMediator mediator, IServiceProvider provider) : base( options, mediator, provider) { Database.EnsureCreated(); }

[MingHuiJian]

是不是Infrastructure没有MediatR 处理程序注册服务注册不了

[witskeeper]

这两行代码顺序错了

var provider = services.BuildServiceProvider();
services.AddMediatR(cfg => cfg.RegisterServicesFromAssemblies(Assembly.GetExecutingAssembly()));、

你应该先 AddMediatR 再 BuildServiceProvider，改成下面这样应该就可以了：

services.AddMediatR(cfg => cfg.RegisterServicesFromAssemblies(Assembly.GetExecutingAssembly()));
var provider = services.BuildServiceProvider();

[MingHuiJian]

可以了，谢谢！