英文:
Problem foreign key between tables in ASP.NET Core 6 MVC & EF Core
问题
我在我的新项目中遇到了问题，我在ASP.NET Core 6和Entity Framework Core中工作。在我的项目中，我有10个表，问题出现在所有表之间的关系上。上次我发布了我的项目的一部分，你提出了一些更改和建议，我做出了更改，但我发现了另一种问题，我努力尝试解决它，但无法解决。
我决定与您分享我的整个项目，我需要一些帮助，请。
这个项目是关于学校管理系统
模型：
public class Classe
{
[Key]
public int Id { get; set; }
public string ClassName { get; set; }
public ICollection<Examen> Examens { get; set; }
public ICollection<Subject> Subjects { get; set; }
public ICollection<Student> Students { get; set; }
public ICollection<TeacherSubject> TeacherSubjects { get; set; }
public ICollection<Expense> Expenses { get; set; }
public ICollection<Fee> Fees { get; set; }
public ICollection<StudentAttendence> StudentAttendence { get; set; }
}
public class Examen
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public int Marks { get; set; }
public virtual Classe Classe { get; set; }
[ForeignKey(nameof(Classe))]
public int ClasseId { get; set; }
public virtual Subject Subject { get; set; }
[ForeignKey(nameof(Subject))]
public int SubjectId { get; set; }
}
// 其余模型类的定义省略
我的DbContext：
public class SchoolContext : DbContext
{
public SchoolContext(DbContextOptions<SchoolContext> options) : base(options)
{
}
public DbSet<Classe> Classes { get; set; }
public DbSet<Examen> Examens { get; set; }
public DbSet<Subject> Subjects { get; set; }
public DbSet<Student> Students { get; set; }
public DbSet<Teacher> Teachers { get; set; }
public DbSet<TeacherSubject> TeacherSubjects { get; set; }
public DbSet<Expense> Expenses { get; set; }
public DbSet<Fee> Fees { get; set; }
public DbSet<StudentAttendence> StudentAttendences { get; set; }
public DbSet<TeacherAttendence> TeacherAttendences { get; set; }
}
当我添加迁移时，我总是遇到这个问题：
引入FOREIGN KEY约束'FK_Examens_Subjects_SubjectId'到'Exams'表可能导致循环或多次级联访问。请指定ON DELETE NO ACTION或ON UPDATE NO ACTION，或修改其他FOREIGN KEY约束。
无法创建约束或索引。
我在Excel中表示了我的数据库。
能否有人帮助我找出如何修复这个问题？
提前感谢！
英文:
I have a problem in my new project, I work in ASP.NET Core 6 and Entity Framework Core. In my project I have 10 tables, the problem comes from the relation between all the tables. Last time I posted a part of my project, you proposed to me some changes and advice, I make the changes but I found another type of problem, I tried very hard to solve it but I cannot.
I decided to share with you all my project and I need some helps please.
The project is about a school management system
Models:
public class Classe
{
[Key]
public int Id { get; set; }
public string ClassName { get; set; }
public ICollection<Examen> Examens { get; set; }
public ICollection<Subject> Subjects { get; set; }
public ICollection<Student> Students { get; set; }
public ICollection<TeacherSubject> TeacherSubjects { get; set; }
public ICollection<Expense> Expenses { get; set; }
public ICollection<Fee> Fees { get; set; }
public ICollection<StudentAttendence> StudentAttendence { get; set; }
}
public class Examen
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public int Marks { get; set; }
public virtual Classe Classe { get; set; }
[ForeignKey(nameof(Classe))]
public int ClasseId { get; set; }
public virtual Subject Subject { get; set; }
[ForeignKey(nameof(Subject))]
public int SubjectId { get; set; }
}
public class Expense
{
public int Id { get; set; }
public int ChargeAmount { get; set; }
public virtual Classe Classe { get; set; }
[ForeignKey(nameof(Classe))]
public int ClasseId { get; set; }
public virtual Subject Subject { get; set; }
[ForeignKey(nameof(Subject))]
public int SubjectId { get; set; }
}
public class Fee
{
public int Id { get; set; }
public int FeeAmount { get; set; }
public virtual Classe Classe { get; set; }
[ForeignKey(nameof(Classe))]
public int ClasseId { get; set; }
}
public class Student
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime DOB { get; set; }
public string Gender { get; set; }
public string Mobile { get; set; }
public string RollNo { get; set; }
public string Adresse { get; set; }
public virtual Classe Classe { get; set; }
[ForeignKey(nameof(Classe))]
public int ClasseId { get; set; }
}
public class StudentAttendence
{
public int Id { get; set; }
public string RollNo { get; set; }
public byte Status { get; set; }
public DateTime date { get; set; }
public virtual Classe Classe { get; set; }
[ForeignKey(nameof(Classe))]
public int ClasseId { get; set; }
public virtual Subject Subject { get; set; }
[ForeignKey(nameof(Subject))]
public int SubjectId { get; set; }
}
public class Subject
{
public int Id { get; set; }
public string SubjectName { get; set; }
public ICollection<Examen> Examens { get; set; }
public ICollection<TeacherSubject> TeacherSubjects { get; set; }
public ICollection<Expense> Expenses { get; set; }
public ICollection<StudentAttendence> StudentAttendence { get; set; }
public virtual Classe Classe { get; set; }
[ForeignKey(nameof(Classe))]
public int ClasseId { get; set; }
}
public class Teacher
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime DOB { get; set; }
public string Gender { get; set; }
public string Mobile { get; set; }
public string Email { get; set; }
public string Adresse { get; set; }
public string PassWord { get; set; }
public ICollection<TeacherSubject> TeacherSubjects { get; set; }
public ICollection<TeacherAttendence> TeacherAttendence { get; set; }
}
public class TeacherAttendence
{
public int Id { get; set; }
public byte Status { get; set; }
public DateTime date { get; set; }
public virtual Teacher Teacher { get; set; }
[ForeignKey(nameof(Teacher))]
public int TeacherId { get; set; }
}
public class TeacherSubject
{
public int Id { get; set; }
public virtual Classe Classe { get; set; }
[ForeignKey(nameof(Classe))]
public int ClasseId { get; set; }
public virtual Subject Subject { get; set; }
[ForeignKey(nameof(Subject))]
public int SubjectId { get; set; }
public virtual Teacher Teacher { get; set; }
[ForeignKey(nameof(Teacher))]
public int TeacherId { get; set; }
}
My DbContext :
public class SchoolContext : DbContext
{
public SchoolContext(DbContextOptions<SchoolContext> options):base(options)
{
}
public DbSet<Classe> Classes { get; set; }
public DbSet<Examen> Examens { get; set; }
public DbSet<Subject> Subjects { get; set; }
public DbSet<Student> Students { get; set; }
public DbSet<Teacher> Teachers { get; set; }
public DbSet<TeacherSubject> TeacherSubjects { get; set; }
public DbSet<Expense> Expenses { get; set; }
public DbSet<Fee> Fees { get; set; }
public DbSet<StudentAttendence> StudentAttendences { get; set; }
public DbSet<TeacherAttendence> TeacherAttendences { get; set; }
}
When I add a migration, I always get this problem :
> Introducing a FOREIGN KEY constraint 'FK_Examens_Subjects_SubjectId' on the 'Exams' table may cause cycles or multiple cascad accesses. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.
> Unable to create constraint or index.
I represented my database in Excel :
Can someone please help me to find how can I fix this ?
Thanks in advance
答案1
得分: 0
与您的多级级联关系存在问题。最简单的方法是取消Classe和Subject之间的关系：
public class Classe
{
[Key]
public int Id { get; set; }
public string ClassName { get; set; }
public ICollection<Examen> Examens { get set; }
//public ICollection<Subject> Subjects { get; set; }
public ICollection<Student> Students { get; set; }
public ICollection<TeacherSubject> TeacherSubjects { get; set; }
public ICollection<Expense> Expenses { get; set; }
public ICollection<Fee> Fees { get; set; }
public ICollection<StudentAttendence> StudentAttendence { get; set; }
}
public class Subject
{
public int Id { get; set; }
public string SubjectName { get; set; }
public ICollection<Examen> Examens { get; set; }
public ICollection<TeacherSubject> TeacherSubjects { get; set; }
public ICollection<Expense> Expenses { get; set; }
public ICollection<StudentAttendence> StudentAttendence { get; set; }
//public virtual Classe Classe { get; set; }
//[ForeignKey(nameof(Classe))]
//public int ClasseId { get; set; }
}
有关详细信息，您可以参考此链接。
英文:
There is a problem with your multi-cascade relationship. The easiest way is to cancel the relationship between Classe and Subject:
public class Classe
{
[Key]
public int Id { get; set; }
public string ClassName { get; set; }
public ICollection<Examen> Examens { get; set; }
//public ICollection<Subject> Subjects { get; set; }
public ICollection<Student> Students { get; set; }
public ICollection<TeacherSubject> TeacherSubjects { get; set; }
public ICollection<Expense> Expenses { get; set; }
public ICollection<Fee> Fees { get; set; }
public ICollection<StudentAttendence> StudentAttendence { get; set; }
}
public class Subject
{
public int Id { get; set; }
public string SubjectName { get; set; }
public ICollection<Examen> Examens { get; set; }
public ICollection<TeacherSubject> TeacherSubjects { get; set; }
public ICollection<Expense> Expenses { get; set; }
public ICollection<StudentAttendence> StudentAttendence { get; set; }
//public virtual Classe Classe { get; set; }
//[ForeignKey(nameof(Classe))]
//public int ClasseId { get; set; }
}
For details, you can refer to this link.
答案2
得分: 0
以下是您提供的代码的翻译部分：
我找到了解决方案，我在我的 DbContext 类中进行了一些更改。
public class SchoolContext : DbContext
{
public SchoolContext(DbContextOptions<SchoolContext> options) : base(options)
{
}
public DbSet<Classe> Classes { get; set; }
public DbSet<Examen> Examens { get; set; }
public DbSet<Subject> Subjects { get; set; }
public DbSet<Student> Students { get; set; }
public DbSet<Teacher> Teachers { get; set; }
public DbSet<Expense> Expenses { get; set; }
public DbSet<Fee> Fees { get; set; }
public DbSet<StudentAttendence> StudentAttendences { get; set; }
public DbSet<TeacherAttendence> TeacherAttendences { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Examen>()
.HasKey(x => new { x.ClasseId, x.SubjectId });
modelBuilder.Entity<Examen>()
.HasOne(x => x.Classe)
.WithMany(z => z.Examens)
.HasForeignKey(x => x.ClasseId)
.OnDelete(DeleteBehavior.ClientSetNull);
modelBuilder.Entity<Examen>()
.HasOne(x => x.Subject)
.WithMany(z => z.Examens)
.HasForeignKey(x => x.SubjectId)
.OnDelete(DeleteBehavior.ClientSetNull);
modelBuilder.Entity<Subject>()
.HasOne(x => x.Classe)
.WithMany(z => z.Subjects)
.HasForeignKey(x => x.ClasseId)
.OnDelete(DeleteBehavior.ClientSetNull);
}
}
希望这对您有所帮助。
英文:
I find the solution, I make some changes in my class DbContext
public class SchoolContext : DbContext
{
public SchoolContext(DbContextOptions<SchoolContext> options) : base(options)
{
}
public DbSet<Classe> Classes { get; set; }
public DbSet<Examen> Examens { get; set; }
public DbSet<Subject> Subjects { get; set; }
public DbSet<Student> Students { get; set; }
public DbSet<Teacher> Teachers { get; set; }
public DbSet<Expense> Expenses { get; set; }
public DbSet<Fee> Fees { get; set; }
public DbSet<StudentAttendence> StudentAttendences { get; set; }
public DbSet<TeacherAttendence> TeacherAttendences { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Examen>().
HasKey(x=> new {x.ClasseId, x.SubjectId});
modelBuilder.Entity<Examen>()
.HasOne(x => x.Classe)
.WithMany(z=>z.Examens)
.HasForeignKey(x=>x.ClasseId)
.OnDelete(DeleteBehavior.ClientSetNull);
modelBuilder.Entity<Examen>()
.HasOne(x => x.Subject)
.WithMany(z => z.Examens)
.HasForeignKey(x => x.SubjectId)
.OnDelete(DeleteBehavior.ClientSetNull);
modelBuilder.Entity<Subject>()
.HasOne(x => x.Classe)
.WithMany(z => z.Subjects)
.HasForeignKey(x => x.ClasseId)
.OnDelete(DeleteBehavior.ClientSetNull);
}
}
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