Question

我安装vs 2017并尝试使用.net core 1.1，实体框架和我的sql数据库创建一个测试web api项目。

bellow是我正在使用的包列表

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

  <PropertyGroup>
    <TargetFramework>netcoreapp1.1</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <Folder Include="wwwroot\" />
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.ApplicationInsights.AspNetCore" Version="2.0.0" />
    <PackageReference Include="Microsoft.AspNetCore" Version="1.1.2" />
    <PackageReference Include="Microsoft.AspNetCore.Mvc" Version="1.1.3" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="1.1.2" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="2.0.0-preview1-final" />
    <PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="1.1.2" />
    <PackageReference Include="MySql.Data.EntityFrameworkCore" Version="7.0.7-m61" />
    <PackageReference Include="Pomelo.EntityFrameworkCore.MySql" Version="1.1.2" />
  </ItemGroup>
  <ItemGroup>
    <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="1.0.1" />
  </ItemGroup>

</Project>

和dbcontext类是

public class NorthWindDBContext : DbContext
    {
        public NorthWindDBContext()
        //: base(options)
        { }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            var builder = new ConfigurationBuilder()
                       .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true);

            var configuration = builder.Build();

            string connectionString = configuration.GetConnectionString("northwindConnection");
            optionsBuilder.UseMySql(connectionString);
        }


        public virtual DbSet<Customers> Customers { get; set; }
        public virtual DbSet<Categories> Categories { get; set; }
        public virtual DbSet<Products> Products { get; set; }
        public virtual DbSet<Orders> Orders { get; set; }
        public virtual DbSet<Order_Details> Order_Details { get; set; }



    }

但是当我尝试运行异常时

System.InvalidOperationException：'实体类型'类别' 需要定义主键。'

我不明白哪里出错了。

请帮助

更新1 贝娄是分类模型

public class Categories
    {
        [Key]
        public int CategoryID { get; set; }
        public string CategoryName { get; set; }
        public string Description { get; set; }
        public byte Picture { get; set; }  

    }

我已经在MySql中创建了数据库。

更新2

 public class Categories
    {
        [DatabaseGenerated(DatabaseGeneratedOption.None)]        
        public int CategoryID { get; set; }
        public string CategoryName { get; set; }
        public string Description { get; set; }
        public byte Picture { get; set; }


    }

更新3

public class Categories
    {
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        [Key]
        public int CategoryID { get; set; }
        public string CategoryName { get; set; }
        public string Description { get; set; }
        public byte Picture { get; set; }
    }

Answer 1

实体类型＆＃39;类别＆＃39; 需要定义主键。

实体框架需要主键才能工作。有两种方法可以做到这一点（我知道）。

例如

//Data Annotations
public class EmployeeEntity : BaseEntity
{
    // Denotes the primary key column
    [Key]
    // Add this if your column is not auto-generated
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public short Id { get; set; }

    public string Name { get; set; }

    // more fields, probably
}

// Fluent API
public partial class EmployeeMap : EntityTypeConfiguration<EmployeeEntity>
{
    public EmployeeMap()
    {
        ToTable("employee");
        HasKey(emp => emp.Id)
          .HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
    }
}

请注意，如果您的主键未自动生成，则需要使用您选择的任何方法告知EF。

注释：[DatabaseGenerated(DatabaseGeneratedOption.None)]
流利：HasKey(emp => emp.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);

.net核心1.1 entityframework和mysql数据库连接

1 个答案: