由于没有系统地学习过EF。就在项目中使用，造成许多莫名的错误。尤其是在复杂对象的存储上，更是伤透脑筋。今天对复杂对象存储作了一个总结。
订单Order->订单项OrderItem->商品Good->零件Part
其中订单和订单项一对多，商品和订单项一对多，商品和零件多对多。
代码：
public class Order
{
[Key()]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
public string Name { get; set; }
public virtual List<OrderItem> OrderItems { get; set; }
public Order()
{
OrderItems = new List<OrderItem>();
}
}
public class OrderItem
{
[Key()]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
public string Name { get; set; }
public int GoodID { get; set; }
public virtual Good Good { get; set; }
public int OrderID { get; set; }
public virtual Order Order { get; set; }
}
public class Good
{
[Key()]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
public string Name { get; set; }
public virtual List<OrderItem> OrderItems { get; set; }
public virtual List<Part> Parts { get; set; }
public Good()
{
OrderItems = new List<OrderItem>();
Parts = new List<Part>();
}
}
public class Part
{
[Key()]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
public string Name { get; set; }
public virtual List<Good> Goods { get; set; }
public Part()
{
Goods = new List<Good>();
}
}
public class CDbContext : DbContext
{
private readonly static string CONNECTION_STRING = "name=Test_ConnString";
public CDbContext()
: base(CONNECTION_STRING)
{
}
public DbSet<Order> OrderSet { get; set; }
public DbSet<OrderItem> OrderItemSet { get; set; }
public DbSet<Good> GoodSet { get; set; }
public DbSet<Part> PartSet { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Order>().HasMany<OrderItem>(i => i.OrderItems)
.WithRequired(i => i.Order).HasForeignKey(i => i.OrderID);
modelBuilder.Entity<OrderItem>().HasRequired<Good>(i => i.Good)
.WithMany(i => i.OrderItems)
.HasForeignKey(i => i.GoodID);
modelBuilder.Entity<Good>().HasMany<Part>(i => i.Parts)
.WithMany(i => i.Goods).Map(i => i.MapLeftKey("GoodID")
.MapRightKey("PartID").ToTable("GoodPart"));
}
}
public class CDbInit : DropCreateDatabaseIfModelChanges<CDbContext>
{
protected override void Seed(CDbContext context)
{
//var part = new Part();
//part.Name = "Part1";
//context.PartSet.Add(part);
//context.SaveChanges();
}
}
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<connectionStrings>
<add name="Test_ConnString"
connectionString="Persist Security Info = true;Data Source=SINPC\SIN2000;Initial Catalog=TestDb;User Id=sa;Password=sa;"
providerName="System.Data.SqlClient"/>
</connectionStrings>
</configuration>
private void button1_Click(object sender, EventArgs e)
{
Part part = new Part();
Good good = new Good();
using (CDbContext context = new CDbContext())
{
part.Name = "part1";
good.Name = "rice1";
good.Parts.Add(part);
Order order = new Order();
order.Name = "order1";
OrderItem item = new OrderItem();
item.Good = good;
item.Order = order;
item.Name = "item1";
order.OrderItems.Add(item);
context.OrderSet.Add(order);
context.SaveChanges();
}
}
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Database.SetInitializer<CDbContext>(new CDbInit());
Application.Run(new Form1());
}
}
代码贴完了。调试心得，要保存一个复杂对象，不需要一个简单对象一个简单对象的保存，EF会自动帮我们把简单对象同时保存。
只需要理清这个复杂对象的一条线，通往各简单对象。就可以实现复杂对象的保存，另外
EF还会自动识别哪些简单对象需要保存，哪些不需要保存。