EF-Core 安裝

1.Tools

dotnet add package Microsoft.EntityFrameworkCore.Tools --version 5.0.6

2.選擇資料庫

SqlServer

dotnet add package Microsoft.EntityFrameworkCore.SqlServer --version 5.0.6

MySQL

dotnet add package Pomelo.EntityFrameworkCore.MySql --version 5.0.0

3.Design

dotnet add package Microsoft.EntityFrameworkCore.Design --version 5.0.6

---

Scaffold

dotnet ef dbcontext scaffold "Server=.\SQLEXPRESS;Database=SchoolDB;Trusted_Connection=True;" Microsoft.EntityFrameworkCore.SqlServer -o Models 

  var test = new PromotionTop();
                test.Id = "1";
                test.Name = "3030";
                var test2 = new PromotionTop();
                test2.InjectFrom(new LoopInjection(new[] {"Name"}), test);
                var test2Id = test2.Id;
                var test2name = test2.Name;

---

Github Sample

EF-Core-First-Sample (opens new window)

dotnet ef migrations add InitialCreate // 創建遷移指令
dotnet ef database update // 利用上面所創的遷移更新

一對一關係

e.g. 一張書桌對應一個學生

C# Class Should Be

public class Desk
{
　　public int Id { get; set; }
　　public string Name { get; set; }
　　
　　public Student Student { get; set; }
}

public class Student
{
　　public int Id { get; set; }
　　public string Name { get; set; }
　　public int DeskID { get; set; }
　　
　　public Desk Desk { get; set; }
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
     modelBuilder.Entity<Student>()
                .HasOne(a => a.Desk)
                .WithOne(b => b.Student)
                .HasForeignKey<Desk>(b => b.Id);
}

SQL Server Should Be

Desk

Id	Name
1001	WeiDesk
2002	LeeDesk

Desk 而言

(PK) : ID

Student

Id	Name	DeskID(FK)
1	Wei	1001
2	Lee	2002

Student 而言

(PK) : ID

(FK) : DeskID

alter table Student
	add constraint FK_Students_Desk_DeskID
		foreign key (DeskID) references Desk

---

一對多關係

e.g. 一間學校有多個老師

C# Class Should Be

public class School
{
　　public int Id { get; set; }
　　public string Name { get; set; }
　　
   public ICollection<Teacher> Teachers { get; set; }
}

public class Teacher
{
　　public int Id { get; set; }
　　public string Name { get; set; }
　　public int SchooldId { get; set; }
　　public School School { get; set; }
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
      modelBuilder.Entity<School>()
                .HasMany(c => c.Teachers)
                .WithOne(e => e.School);
}

SQL Server Should Be

Teacher(多方)

Id	Name	SchoolId(FK)
1	林老師	A01
2	王老師	B01

Teacher而言

(PK) : ID

(FK): SchoolID

alter table Teacher
	add constraint FK_Teacher_School_SchoolId
		foreign key (SchoolId) references School (Id)

School(一方)

Id	Name
A01	常春藤大學
B01	台北大學

---

多對多關係

班級和老師的關係 (老師可以去多個班級任教) 實現: 需使用獨立一張表實現

C# Classm Should Be

public class Teacher
{
        public int TeacherId { get; set; }
        public string Name { get; set; }
        public IEnumerable<TeacherClassRoom> ClassRooms { get; set; }
}

    public class ClassRoom
    {
        public int ClassRoomId { get; set; }
        public string CategoryName { get; set; }
        public IEnumerable<TeacherClassRoom> Teachers { get; set; }
    }

    public class TeacherClassRoom
    {
        public int TeacherId { get; set; }
        public Teacher Teacher { get; set; }
        public int ClassRoomId { get; set; }
        public ClassRoom ClassRoom { get; set; }
    }

  protected override void OnModelCreating(ModelBuilder modelBuilder)
        { 
            modelBuilder.Entity<TeacherClassRoom>()
                .HasKey(bc => new { bc.TeacherId, bc.ClassRoomId });  
            modelBuilder.Entity<TeacherClassRoom>()
                .HasOne(bc => bc.Teacher)
                .WithMany(b => b.ClassRooms)
                .HasForeignKey(bc => bc.TeacherId);  
            modelBuilder.Entity<TeacherClassRoom>()
                .HasOne(bc => bc.ClassRoom)
                .WithMany(c => c.Teachers)
                .HasForeignKey(bc => bc.ClassRoomId);

        }

SQL Server Should Be

Teacher (教師表)

Id	Name
1	林老師
2	王老師

ClassRoom (班級表)

Id	Name
C01	三年一班
C02	三年二班

ClassRoomTeacher (班級教師表)

TeacherId(PK)	ClassRoomId(PK)
1	C01
2	C02

ClassRoomTeacher而言

create table TeacherClassRoom
(
    TeacherId   int not null
        constraint FK_TeacherClassRoom_Teacher_TeacherId
            references Teacher
            on delete cascade,
    ClassRoomId int not null
        constraint FK_TeacherClassRoom_ClassRoom_ClassRoomId
            references ClassRoom
            on delete cascade,
    constraint PK_TeacherClassRoom
        primary key (TeacherId, ClassRoomId)
)
go

create index IX_TeacherClassRoom_ClassRoomId
    on TeacherClassRoom (ClassRoomId)
go