第一步：创建两个项目(类库：CodeFirst_Entity  控制台：Test)
第二步：在控制台项目右键-管理NuGet程序包中安装EntityFramework
第三步：在控制台app.config中添加节点
  <connectionStrings>
    <add name="EFContext" connectionString="server=.;uid=sa;pwd=******;database=test_db"
                                                                               providerName="System.Data.SqlClient"/>
  </connectionStrings>
第四步：在类库项目中应用EntityFramework.dll  //单层开发该步骤省略
第五步：在类库项目(Entity)中创建实体类
             (注意属性:产品类外键必须是产品类型类名+Id   如：ProductTypeId)
第六步：添加自定义上下文类EFContext 并继承框架的接口DbContext
             提示：关联实体类 public DbSet<Product> Products { get; set; }
    public class EFContext : DbContext
    {
        public DbSet<Product> Products { get; set; }
        public DbSet<ProductType> ProductTypes { get; set; }
    }

using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EF_Demo_02.Entity.Models
{
    public class ProductType
    {
        public int ProductTypeId { get; set; }//主表主键

        /// <summary>
        /// 类型名称
        /// </summary>
        public string TypeName { get; set; }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EF_Demo_02.Entity.Models
{
    public class Product
    {
        public int ProductId { get; set; }
        public string ProductName { get; set; }
        public double Price { get; set; }
        public string Description { get; set; }
        public DateTime CreateTime { get; set; }
        public int ProductTypeId { get; set; }


        /// <summary>
        /// 一对一关系
        /// </summary>
        public ProductType ProductType { get; set; }

    }
}

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EF_Demo_02.Entity.Models
{
    public class EFContext:DbContext//数据库上下文，全局配置
    {
        public DbSet<Product> Products { get; set; }
        public DbSet<ProductType> ProductTypes { get; set; }
    }
}

using EF_Demo_02.Entity.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EF_Demo_02.Entity.DAL
{
    public class ProductTypeService
    {
        public bool Add(ProductType productType)
        {
            int result = 0;
            using (EFContext db = new EFContext())
            {
                db.ProductTypes.Add(productType);
                result = db.SaveChanges();
            }
            return result > 0;
        }
    }
}

using EF_Demo_02.Entity.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EF_Demo_02.Entity.DAL
{
    public class ProductServices
    {
        public bool Add(Product product)
        {
            int result = 0;
            using (EFContext db = new EFContext())
            {
                db.Products.Add(product);
                result = db.SaveChanges();
            }
            return result > 0;
        }
    }
}

App.config

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
        <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
        <section name="entityFramework"
          type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
          requirePermission="false"/>
    </configSections>
  <connectionStrings>
    <add name="EFContext" connectionString="server=.;uid=sa;pwd=adminsystem;database=TaoBao" providerName="System.Data.SqlClient" />
  </connectionStrings>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1"/>
    </startup>
    <entityFramework>
        <providers>
            <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer"/>
        </providers>
    </entityFramework>
</configuration>

using EF_Demo_02.Entity.DAL;
using EF_Demo_02.Entity.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EF_Demo
{
    class Program
    {
        static void Main(string[] args)
        {
            ProductTypeService productTypeService = new ProductTypeService();
            ProductServices productServices = new ProductServices();

            productTypeService.Add(new ProductType() { ProductTypeId=1,TypeName="手机"});
            productServices.Add(new Product() { ProductId=1001,ProductName="华为p20",Description="测试描述",CreateTime=DateTime.Now,Price=1000,ProductTypeId=1});
        }
    }
}