C# 首先创建代码,多对多,并在关联表中添加其他字段
我有这样一个场景:C# 首先创建代码,多对多,并在关联表中添加其他字段,c#,entity-framework,ef-code-first,many-to-many,C#,Entity Framework,Ef Code First,Many To Many,我有这样一个场景: public class Member { public int MemberID { get; set; } public string FirstName { get; set; } public string LastName { get; set; } public virtual ICollection<Comment> Comments { get; set; } } public class Comment {
public class Member
{
public int MemberID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public virtual ICollection<Comment> Comments { get; set; }
}
public class Comment
{
public int CommentID { get; set; }
public string Message { get; set; }
public virtual ICollection<Member> Members { get; set; }
}
public class MemberComment
{
public int MemberID { get; set; }
public int CommentID { get; set; }
public int Something { get; set; }
public string SomethingElse { get; set; }
}
公共类成员
{
public int MemberID{get;set;}
公共字符串名{get;set;}
公共字符串LastName{get;set;}
公共虚拟ICollection注释{get;set;}
}
公开课评论
{
public int CommentID{get;set;}
公共字符串消息{get;set;}
公共虚拟ICollection成员{get;set;}
}
公共类成员评论
{
public int MemberID{get;set;}
public int CommentID{get;set;}
public int Something{get;set;}
公共字符串SomethingElse{get;set;}
}
如何配置与的关联?还是有更好的方法来创建关联表?不可能使用自定义联接表创建多对多关系。在多对多关系中,EF管理内部和隐藏的联接表。它是模型中没有实体类的表。要使用这种具有附加属性的联接表,您必须实际创建两个一对多关系。它可能是这样的:
public class Member
{
public int MemberID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public virtual ICollection<MemberComment> MemberComments { get; set; }
}
public class Comment
{
public int CommentID { get; set; }
public string Message { get; set; }
public virtual ICollection<MemberComment> MemberComments { get; set; }
}
public class MemberComment
{
[Key, Column(Order = 0)]
public int MemberID { get; set; }
[Key, Column(Order = 1)]
public int CommentID { get; set; }
public virtual Member Member { get; set; }
public virtual Comment Comment { get; set; }
public int Something { get; set; }
public string SomethingElse { get; set; }
}
var commentsOfMembers = context.Members
.Where(m => m.LastName == "Smith")
.SelectMany(m => m.MemberComments.Select(mc => mc.Comment))
.ToList();
。。。或者
var commentsOfMembers = context.MemberComments
.Where(mc => mc.Member.LastName == "Smith")
.Select(mc => mc.Comment)
.ToList();
或者,要创建名为“Smith”(我们假设不止一个)的成员列表及其评论,您可以使用投影:
var membersWithComments = context.Members
.Where(m => m.LastName == "Smith")
.Select(m => new
{
Member = m,
Comments = m.MemberComments.Select(mc => mc.Comment)
})
.ToList();
如果要查找MemberId
=1的成员的所有注释:
var commentsOfMember = context.MemberComments
.Where(mc => mc.MemberId == 1)
.Select(mc => mc.Comment)
.ToList();
现在,您还可以根据联接表中的属性进行筛选(这在多对多关系中是不可能的),例如:筛选成员1中属性为99的所有注释Something
:
var filteredCommentsOfMember = context.MemberComments
.Where(mc => mc.MemberId == 1 && mc.Something == 99)
.Select(mc => mc.Comment)
.ToList();
由于延迟加载,事情可能会变得更容易。如果您有一个已加载的成员
,您应该能够在无需显式查询的情况下获取注释:
var commentsOfMember = member.MemberComments.Select(mc => mc.Comment);
我猜延迟加载会在幕后自动获取评论
编辑
为了好玩,我们提供了几个示例,介绍如何在此模型中添加实体和关系以及如何删除它们:
1) 创建此成员的一个成员和两个注释:
var member1 = new Member { FirstName = "Pete" };
var comment1 = new Comment { Message = "Good morning!" };
var comment2 = new Comment { Message = "Good evening!" };
var memberComment1 = new MemberComment { Member = member1, Comment = comment1,
Something = 101 };
var memberComment2 = new MemberComment { Member = member1, Comment = comment2,
Something = 102 };
context.MemberComments.Add(memberComment1); // will also add member1 and comment1
context.MemberComments.Add(memberComment2); // will also add comment2
context.SaveChanges();
2) 添加member1的第三条注释:
var member1 = context.Members.Where(m => m.FirstName == "Pete")
.SingleOrDefault();
if (member1 != null)
{
var comment3 = new Comment { Message = "Good night!" };
var memberComment3 = new MemberComment { Member = member1,
Comment = comment3,
Something = 103 };
context.MemberComments.Add(memberComment3); // will also add comment3
context.SaveChanges();
}
3) 创建新成员并将其与现有注释2关联:
var comment2 = context.Comments.Where(c => c.Message == "Good evening!")
.SingleOrDefault();
if (comment2 != null)
{
var member2 = new Member { FirstName = "Paul" };
var memberComment4 = new MemberComment { Member = member2,
Comment = comment2,
Something = 201 };
context.MemberComments.Add(memberComment4);
context.SaveChanges();
}
4) 在现有成员2和成员3之间创建关系:
var member2 = context.Members.Where(m => m.FirstName == "Paul")
.SingleOrDefault();
var comment3 = context.Comments.Where(c => c.Message == "Good night!")
.SingleOrDefault();
if (member2 != null && comment3 != null)
{
var memberComment5 = new MemberComment { Member = member2,
Comment = comment3,
Something = 202 };
context.MemberComments.Add(memberComment5);
context.SaveChanges();
}
5) 再次删除此关系:
var memberComment5 = context.MemberComments
.Where(mc => mc.Member.FirstName == "Paul"
&& mc.Comment.Message == "Good night!")
.SingleOrDefault();
if (memberComment5 != null)
{
context.MemberComments.Remove(memberComment5);
context.SaveChanges();
}
6) 删除member1及其与注释的所有关系:
var member1 = context.Members.Where(m => m.FirstName == "Pete")
.SingleOrDefault();
if (member1 != null)
{
context.Members.Remove(member1);
context.SaveChanges();
}
这也会删除
MemberComments
中的关系,因为MemberComments
和MemberComments
之间以及Comment
和MemberComments
之间的一对多关系是按约定级联删除的。这种情况是因为MemberComment
中的MemberId
和CommentId
被检测为Member
和Comment
导航属性的外键属性,并且由于FK属性的类型为non-nullableint
,因此需要关系,从而最终导致级联删除设置。我认为,在这个模型中是有意义的。我将使用fluent映射发布代码
公共类用户{
public int UserID{get;set;}
公共字符串用户名{get;set;}
公共字符串密码{get;set;}
公共ICollection用户电子邮件{get;set;}
}
公共类电子邮件{
public int EmailID{get;set;}
公共字符串地址{get;set;}
公共ICollection用户电子邮件{get;set;}
}
公共类用户电子邮件{
public int UserID{get;set;}
public int EmailID{get;set;}
公共bool IsPrimary{get;set;}
}
在DbContext
派生类上,可以执行以下操作:
公共类MyContext:DbContext{
模型创建时受保护的覆盖无效(DbModelBuilder builder){
//主键
builder.Entity().HasKey(q=>q.UserID);
builder.Entity().HasKey(q=>q.EmailID);
builder.Entity().HasKey(q=>
新{
q、 UserID,q.EmailID
});
//关系
builder.Entity()
.HasRequired(t=>t.Email)
.WithMany(t=>t.useremail)
.HasForeignKey(t=>t.EmailID)
builder.Entity()
.HasRequired(t=>t.User)
.WithMany(t=>t.useremail)
.HasForeignKey(t=>t.UserID)
}
}
它的效果与另一种方法相同,即更好或更差。这个方法是正确的,但不完整,我已经测试过了。“UserEmail”类中缺少属性:
如果有人感兴趣,我会发布我测试过的代码。
问候
使用System.Data.Entity;
使用制度;
使用System.Collections.Generic;
使用System.ComponentModel.DataAnnotations;
使用System.ComponentModel.DataAnnotations.Schema;
使用System.Linq;
使用System.Web;
#区域示例2
公共类用户测试
{
public int UserTestID{get;set;}
公共字符串UserTestname{get;set;}
公共字符串密码{get;set;}
公共ICollection UserTestEmailTests{get;set;}
公共静态void DoSomeTest(ApplicationDbContext上下文)
{
对于(int i=0;i<5;i++)
{
var user=context.UserTest.Add(new UserTest(){UserTestname=“Test”+i});
var address=context.EmailTest.Add(new-EmailTest(){address=“address@”+i});
}
SaveChanges();
foreach(context.UserTest.Include中的var user(t=>t.UserTestEmailTests))
{
foreach(context.EmailTest中的var地址)
{
user.UserTestEmailTests.Add(新的UserTestEmailTest(){UserTest=user,EmailTest=address,n1=user.UserTestID,n2=address.EmailTestID});
}
}
SaveChanges();
}
}
公共类电子邮件测试
{
public int EmailTestID{get;set;}
公共字符串地址{get;set;}
公共ICollection UserTestEmailTests{get;set;}
}
公共类UserTestEmail
public UserTest UserTest { get; set; }
public EmailTest EmailTest { get; set; }
using System.Data.Entity;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Web;
#region example2
public class UserTest
{
public int UserTestID { get; set; }
public string UserTestname { get; set; }
public string Password { get; set; }
public ICollection<UserTestEmailTest> UserTestEmailTests { get; set; }
public static void DoSomeTest(ApplicationDbContext context)
{
for (int i = 0; i < 5; i++)
{
var user = context.UserTest.Add(new UserTest() { UserTestname = "Test" + i });
var address = context.EmailTest.Add(new EmailTest() { Address = "address@" + i });
}
context.SaveChanges();
foreach (var user in context.UserTest.Include(t => t.UserTestEmailTests))
{
foreach (var address in context.EmailTest)
{
user.UserTestEmailTests.Add(new UserTestEmailTest() { UserTest = user, EmailTest = address, n1 = user.UserTestID, n2 = address.EmailTestID });
}
}
context.SaveChanges();
}
}
public class EmailTest
{
public int EmailTestID { get; set; }
public string Address { get; set; }
public ICollection<UserTestEmailTest> UserTestEmailTests { get; set; }
}
public class UserTestEmailTest
{
public int UserTestID { get; set; }
public UserTest UserTest { get; set; }
public int EmailTestID { get; set; }
public EmailTest EmailTest { get; set; }
public int n1 { get; set; }
public int n2 { get; set; }
//Call this code from ApplicationDbContext.ConfigureMapping
//and add this lines as well:
//public System.Data.Entity.DbSet<yournamespace.UserTest> UserTest { get; set; }
//public System.Data.Entity.DbSet<yournamespace.EmailTest> EmailTest { get; set; }
internal static void RelateFluent(System.Data.Entity.DbModelBuilder builder)
{
// Primary keys
builder.Entity<UserTest>().HasKey(q => q.UserTestID);
builder.Entity<EmailTest>().HasKey(q => q.EmailTestID);
builder.Entity<UserTestEmailTest>().HasKey(q =>
new
{
q.UserTestID,
q.EmailTestID
});
// Relationships
builder.Entity<UserTestEmailTest>()
.HasRequired(t => t.EmailTest)
.WithMany(t => t.UserTestEmailTests)
.HasForeignKey(t => t.EmailTestID);
builder.Entity<UserTestEmailTest>()
.HasRequired(t => t.UserTest)
.WithMany(t => t.UserTestEmailTests)
.HasForeignKey(t => t.UserTestID);
}
}
#endregion
public class Member
{
public int MemberID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public virtual ICollection<Comment> Comments { get; set; }
public virtual ICollection<MemberCommentView> MemberComments { get; set; }
}
public class Comment
{
public int CommentID { get; set; }
public string Message { get; set; }
public virtual ICollection<Member> Members { get; set; }
public virtual ICollection<MemberCommentView> MemberComments { get; set; }
}
public class MemberCommentView
{
public int MemberID { get; set; }
public int CommentID { get; set; }
public int Something { get; set; }
public string SomethingElse { get; set; }
public virtual Member Member { get; set; }
public virtual Comment Comment { get; set; }
}
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity.ModelConfiguration;
public class MemberConfiguration : EntityTypeConfiguration<Member>
{
public MemberConfiguration()
{
HasKey(x => x.MemberID);
Property(x => x.MemberID).HasColumnType("int").IsRequired();
Property(x => x.FirstName).HasColumnType("varchar(512)");
Property(x => x.LastName).HasColumnType("varchar(512)")
// configure many-to-many through internal EF EntitySet
HasMany(s => s.Comments)
.WithMany(c => c.Members)
.Map(cs =>
{
cs.ToTable("MemberComment");
cs.MapLeftKey("MemberID");
cs.MapRightKey("CommentID");
});
}
}
public class CommentConfiguration : EntityTypeConfiguration<Comment>
{
public CommentConfiguration()
{
HasKey(x => x.CommentID);
Property(x => x.CommentID).HasColumnType("int").IsRequired();
Property(x => x.Message).HasColumnType("varchar(max)");
}
}
public class MemberCommentViewConfiguration : EntityTypeConfiguration<MemberCommentView>
{
public MemberCommentViewConfiguration()
{
ToTable("MemberCommentView");
HasKey(x => new { x.MemberID, x.CommentID });
Property(x => x.MemberID).HasColumnType("int").IsRequired();
Property(x => x.CommentID).HasColumnType("int").IsRequired();
Property(x => x.Something).HasColumnType("int");
Property(x => x.SomethingElse).HasColumnType("varchar(max)");
// configure one-to-many targeting the Join Table view
// making all of its properties available
HasRequired(a => a.Member).WithMany(b => b.MemberComments);
HasRequired(a => a.Comment).WithMany(b => b.MemberComments);
}
}
using System.Data.Entity;
public class MyContext : DbContext
{
public DbSet<Member> Members { get; set; }
public DbSet<Comment> Comments { get; set; }
public DbSet<MemberCommentView> MemberComments { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Configurations.Add(new MemberConfiguration());
modelBuilder.Configurations.Add(new CommentConfiguration());
modelBuilder.Configurations.Add(new MemberCommentViewConfiguration());
OnModelCreatingPartial(modelBuilder);
}
}
var commentsOfMembers = context.Members
.Where(m => m.LastName == "Smith")
.SelectMany(m => m.MemberComments.Select(mc => mc.Comment))
.ToList();
var commentsOfMembers = context.Members
.Where(m => m.LastName == "Smith")
.SelectMany(m => m.Comments)
.ToList();
var membersWithComments = context.Members
.Where(m => m.LastName == "Smith")
.Select(m => new
{
Member = m,
Comments = m.MemberComments.Select(mc => mc.Comment)
})
.ToList();
var membersWithComments = context.Members
.Where(m => m.LastName == "Smith")
.Select(m => new
{
Member = m,
m.Comments
})
.ToList();
var comment = ... // assume comment from member John Smith
var member = ... // assume member John Smith
member.Comments.Remove(comment);
var member = context.Members
.Where(m => m.FirstName == "John", m.LastName == "Smith")
.Include(m => m.Comments);