asp.net mvc code first实体关系一对一、一对多、多对多的设置方法

摘要: 在asp.net mvc code first开发过程中，导航属性的设置很重要，我们实现的一些功能都依赖于导航属性，这里总结了导航属性设置的方法。

1、EF Code First一对一关联关系

　　项目结构图：



　　实体类：

　　Account.cs

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

namespace Northwind.App.Entities
{
public class Account
{
/// <summary>
/// 账户ID
/// </summary>
public int AccountID { get; set; }

/// <summary>
/// 账户名
/// </summary>
public string AccountName { get; set; }

/// <summary>
/// 密码
/// </summary>
public string Password { get; set; }

/// <summary>
/// 用户信息
/// </summary>
public virtual User User { get; set; }
}
}

　　User.cs

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

namespace Northwind.App.Entities
{
public class Account
{
/// <summary>
/// 账户ID
/// </summary>
public int AccountID { get; set; }

/// <summary>
/// 账户名
/// </summary>
public string AccountName { get; set; }

/// <summary>
/// 密码
/// </summary>
public string Password { get; set; }

/// <summary>
/// 用户信息
/// </summary>
public virtual User User { get; set; }
}
}

　　实体映射类：

　　AccountMap.cs

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

using System.Data.Entity.ModelConfiguration;
using System.ComponentModel.DataAnnotations.Schema;

using Northwind.App.Entities;

namespace Northwind.App.Mapping
{
public class AccountMap : EntityTypeConfiguration<Account>
{
public AccountMap()
{
// Primary Key
this.HasKey(t => t.AccountID);

// Properties
this.Property(t => t.AccountName).HasMaxLength(50);
this.Property(t => t.Password).HasMaxLength(100);

// Table & Column Mappings
this.ToTable("Account");
this.Property(t => t.AccountID).HasColumnName("AccountID");
this.Property(t => t.AccountName).HasColumnName("AccountName");
this.Property(t => t.Password).HasColumnName("Password");
}
}
}

　　UserMap.cs

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

using System.Data.Entity.ModelConfiguration;
using System.ComponentModel.DataAnnotations.Schema;

using Northwind.App.Entities;

namespace Northwind.App.Mapping
{
public class UserMap : EntityTypeConfiguration<User>
{
public UserMap()
{
// Primary Key
this.HasKey(t => t.AccountID);

// Properties
this.Property(t => t.AccountID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
this.Property(t => t.UserName).HasMaxLength(50);
this.Property(t => t.Email).HasMaxLength(100);

// Table & Column Mappings
this.ToTable("User");
this.Property(t => t.AccountID).HasColumnName("AccountID");
this.Property(t => t.UserName).HasColumnName("UserName");
this.Property(t => t.Email).HasColumnName("Email");
this.Property(t => t.RegisterDate).HasColumnName("RegisterDate");

// Relationships
this.HasRequired(t => t.Account)
.WithRequiredDependent(t => t.User);
}
}
}

　　NorthwindContext.cs

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

using System.Data.Entity;

using Northwind.App.Entities;
using Northwind.App.Mapping;

namespace Northwind.App
{
public class NorthwindContext : DbContext
{
static NorthwindContext()
{
Database.SetInitializer(new DropCreateDatabaseIfModelChanges<NorthwindContext>());
}

public DbSet<Account> Accounts { get; set; }
public DbSet<User> Users { get; set; }

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add(new AccountMap());
modelBuilder.Configurations.Add(new UserMap());
}
}
}

　　Program.cs

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

using Northwind.App.Entities;

namespace Northwind.App
{
class Program
{
static void Main(string[] args)
{
using (NorthwindContext db = new NorthwindContext())
{
Account account = new Account { AccountName = "Test", Password = "1" };
db.Accounts.Add(account);

User user = new User { AccountID = account.AccountID, UserName = "测试", Email = "test@126.com", RegisterDate = DateTime.Now };
db.Users.Add(user);

db.SaveChanges();
}
}
}
}

　　代码运行后生成的数据库结构图：



2、EF Code First一对多关联关系

　　关联表：Product 产品表、Category分类表

　　关联关系：一个产品属于一个分类，一个分类可以有多个产品

　　实体代码：

　　Category.cs

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

namespace Northwind.App.Entities
{
public class Category
{
/// <summary>
/// 分类ID
/// </summary>
public Guid CategoryID { get; set; }

/// <summary>
/// 分类名称
/// </summary>
public string CategoryName { get; set; }

/// <summary>
/// 产品
/// </summary>
public virtual ICollection<Product> Products { get; set; }
}
}

　　Product.cs

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

namespace Northwind.App.Entities
{
public class Product
{
/// <summary>
/// 产品ID
/// </summary>
public Guid ProductID { get; set; }

/// <summary>
/// 产品名称
/// </summary>
public string ProductName { get; set; }

/// <summary>
/// 单价
/// </summary>
public decimal UnitPrice { get; set; }

/// <summary>
/// 数量
/// </summary>
public Nullable<int> Quantity { get; set; }

/// <summary>
/// 库存
/// </summary>
public Nullable<int> UnitsInStock { get; set; }

/// <summary>
/// 产品类别ID
/// </summary>
public Guid CategoryID { get; set; }

/// <summary>
/// 产品类别
/// </summary>
public virtual Category Category { get; set; }
}
}

　　实体映射类：

　　CategoryMap.cs

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

using System.Data.Entity.ModelConfiguration;
using System.ComponentModel.DataAnnotations.Schema;

using Northwind.App.Entities;

namespace Northwind.App.Mapping
{
public class CategoryMap : EntityTypeConfiguration<Category>
{
public CategoryMap()
{
// Primary Key
this.HasKey(t => t.CategoryID);

// Properties
this.Property(t => t.CategoryID)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
this.Property(t => t.CategoryName).IsRequired()
.HasMaxLength(100);

// Table & Column Mappings
this.ToTable("Category");
this.Property(t => t.CategoryID).HasColumnName("CategoryID");
this.Property(t => t.CategoryName).HasColumnName("CategoryName");
}
}
}

　　ProductMap.cs

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

using System.Data.Entity.ModelConfiguration;
using System.ComponentModel.DataAnnotations.Schema;

using Northwind.App.Entities;

namespace Northwind.App.Mapping
{
public class ProductMap : EntityTypeConfiguration<Product>
{
public ProductMap()
{
// Primary Key
this.HasKey(t => t.ProductID);

// Properties
this.Property(t => t.ProductID)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
this.Property(t => t.ProductName).IsRequired()
.HasMaxLength(100);
this.Property(t => t.UnitPrice).HasPrecision(10, 2);

// Table & Column Mappings
this.ToTable("Product");
this.Property(t => t.ProductID).HasColumnName("ProductID");
this.Property(t => t.ProductName).HasColumnName("ProductName");
this.Property(t => t.UnitPrice).HasColumnName("UnitPrice");
this.Property(t => t.Quantity).HasColumnName("Quantity");
this.Property(t => t.UnitsInStock).HasColumnName("UnitsInStock");
this.Property(t => t.CategoryID).HasColumnName("CategoryID");

// Relationships
this.HasRequired(t => t.Category)
.WithMany(t => t.Products)
.HasForeignKey(t => t.CategoryID)
.WillCascadeOnDelete(false);
}
}
}

　　NorthwindContext.cs

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

using System.Data.Entity;

using Northwind.App.Entities;
using Northwind.App.Mapping;

namespace Northwind.App
{
public class NorthwindContext : DbContext
{
static NorthwindContext()
{
Database.SetInitializer(new DropCreateDatabaseIfModelChanges<NorthwindContext>());
}

public DbSet<Account> Accounts { get; set; }
public DbSet<User> Users { get; set; }
public DbSet<Category> Categories { get; set; }
public DbSet<Product> Products { get; set; }

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add(new AccountMap());
modelBuilder.Configurations.Add(new UserMap());
modelBuilder.Configurations.Add(new CategoryMap());
modelBuilder.Configurations.Add(new ProductMap());
}
}
}

　　Program.cs

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

using Northwind.App.Entities;

namespace Northwind.App
{
class Program
{
static void Main(string[] args)
{
using (NorthwindContext db = new NorthwindContext())
{
Category category = new Category { CategoryName = "手机数码" };
db.Categories.Add(category);

Product product = new Product { CategoryID = category.CategoryID, ProductName = "IPhone5", UnitPrice = 5000m, Quantity = 100, UnitsInStock = 60 };
db.Products.Add(product);

db.SaveChanges();
}
}
}
}

　　运行代码后生成的数据表：