值不能为空.(参数'key')在ASP.NET Core 3..0中

本文介绍了值不能为空.(参数'key')在ASP.NET Core 3..0中的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我需要在ASP.NET Core 3.0中以代码优先的方式创建数据库

I need to create a database with code-first in ASP.NET Core 3.0

这是 DbContext :

public class TrelloContext : DbContext
{
    public TrelloContext(DbContextOptions options) : base(options)
    {
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        modelBuilder.AddDbSet<IEntity>(typeof(IEntity).Assembly);
        modelBuilder.ApplyConfigurationsFromAssembly(typeof(IType).Assembly);
    }
}

这是启动:

public void ConfigureServices(IServiceCollection services)
{
        services.AddControllers().AddControllersAsServices();
        services.AddDbContext<TrelloContext>(options => options.UseSqlServer(Configuration.GetConnectionString("SqlServer")));
        services.Injection();
}

这是我的连接字符串:

"ConnectionStrings": {
    "SqlServer": "Data Source=.;Initial Catalog=TrelloDB;Trusted_Connection=True;Trusted_Connection=True;"
}

当我使用此 add-migration initial 时，出现此错误:

When I use this add-migration initial, I get this error:

出什么问题了?我该如何解决?

What's the problem? How can I solve this?

推荐答案

这是因为您的一个实体(从接口: IEntity 继承)没有标识列.

It was because of one of your entities (inherited from interface: IEntity) do not have an identity column.

请检查所有实体.确保它们都有一个ID或标记为 [Key] 的属性.

Please check all your entites. Make sure they all have an ID or a property marked as [Key].

public class MyEntity : IEntity
{
    // make sure:
    public int Id { get; set; }
    // or:
    [Key]
    public int SomeProperty { get; set; }
}

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