要在數(shù)據(jù)庫中配置一對多關(guān)系，我們可以依賴EF約定，還可以使用數(shù)據(jù)注解或Fluent API來顯式創(chuàng)建關(guān)系。接下來使用捐贈者Donator和支付方法PayWay這兩個類來舉例子,這里的一對多關(guān)系是：一個人可以通過多種支付方式贊助我。

支付方式類PayWay結(jié)構(gòu)如下：

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

namespace OneToMany.Model.Model
{
    public class PayWay
    {
        public int PayWayId { get; set; }

        public string Name { get; set; }

        public virtual Donator Donator { get; set; }
    }
}

因為一個贊助者可以通過多種支付方式贊助我，這句話就表明了Donator對象應(yīng)該有一個PayWay的集合，因此，我們要給Donator類新加入一個集合屬性，捐贈者類Donator結(jié)構(gòu)如下：

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

namespace OneToMany.Model.Model
{
    public class Donator
    {
        public int Id { get; set; }

        public string Name { get; set; }

        public string Amount { get; set; }

        public DateTime DonateDate { get; set; }

        /// <summary>
        /// PayWay類型的集合屬性
        /// </summary>
        public virtual ICollection<PayWay> PayWays { get; set; }
    }
}

Donator類的配置伙伴類的定義如下：

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

namespace OneToMany.Map.Map
{
    public class DonatorMap :EntityTypeConfiguration<Donator>
    {
        public DonatorMap()
        {
            ToTable("Donator");
            //將Name設(shè)置為必須
            this.Property(p => p.Name).IsRequired();
        }

    }
}

PayWay的配置伙伴類的定義如下：

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

namespace OneToMany.Map.Map
{
    public class PayWayMap : EntityTypeConfiguration<PayWay>
    {
        public PayWayMap()
        {
            ToTable("PayWay");
            this.Property(p => p.Name).HasMaxLength(16);
        }
    }
}

EFDbContext類定義如下：

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

namespace OneToMany.Map.EFContext
{
    public class EFDbContext:DbContext
    {
        public EFDbContext()
            : base("name=CodeFirstApplication")
        { }

        public DbSet<PayWay> PayWays { get; set; }
        public DbSet<Donator> Donators { get; set; }


        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            // 設(shè)置主鍵
            modelBuilder.Entity<PayWay>().HasKey(p => p.PayWayId);
            modelBuilder.Entity<Donator>().HasKey(p => p.DonatorId);
            // 設(shè)置一對多
            modelBuilder.Entity<Donator>().HasMany(p => p.PayWays).WithRequired(t => t.Donator);
            base.OnModelCreating(modelBuilder);
        }
    }
}

控制臺程序定義如下：

using OneToMany.Map.EFContext;
using OneToMany.Model.Model;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace OneToManyApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var context = new EFDbContext())
            {
                var donator = new Donator
                {
                    Amount = 6,
                    Name = "蝦米",
                    DonateDate = DateTime.Now,
                    PayWays = new List<PayWay> {
                      new PayWay{Name="支付寶"},
                      new PayWay{Name="微信"}

                    }
                };
                context.Donators.Add(donator);
                context.SaveChanges();
            }

            Console.WriteLine("執(zhí)行成功");
            Console.ReadKey();
        }
    }
}

程序運行后數(shù)據(jù)庫結(jié)構(gòu)如下：