如何修复 Entity Framework Core 中 X 类型错误的“无法确定导航 X 表示的关系”

Question

我正在使用 Entity Framework Core 开发一个 ASP.NET Core 5 项目。

我有这些实体

public class StudentTrainingMark
{
        public         int           Id              { get; set; }
        public         decimal       TheoreticalMark { get; set; }
        public         decimal       PracticalMark   { get; set; }
        public         string        Note            { get; set; }

        public         string        BranchId        { get; set; }
        public         byte          FormationYearId { get; set; } 
        public         string        StudentId       { get; set; }

        public virtual Branch        Branch          { get; set; }
        public virtual FormationYear FormationYear   { get; set; }
        public virtual Student       Student         { get; set; }
}

public class Student
{ 
    public string Id         { get; set; }
    public string FirstName  { get; set; }
    public string FamilyName { get; set; }

    public virtual ICollection<StudentTrainingMark>   StudentTrainingMarks { get; set; }
}

我为每个实体创建了配置文件来执行一些配置，例如必填字段和关系。

所以StudentTrainingMark 也有这样的配置文件：

public class StudentTrainingMarkEntityConfig:IEntityTypeConfiguration<StudentTrainingMark>
{
    public void Configure( EntityTypeBuilder<StudentTrainingMark> builder )
    {
        builder.HasKey( x => x.Id );
        builder.Property( x => x.Id ).UseIdentityColumn();

        builder.Property( x => x.TheoreticalMark ).IsRequired();
        builder.Property( x => x.PracticalMark ).IsRequired();

        builder.Property( x => x.BranchId ).IsRequired();
        builder.Property( x => x.FormationYearId ).IsRequired();
        builder.Property( x => x.StudentId ).IsRequired();
    }
}

Student 也有这样的配置文件：

public class StudentEntityConfig:IEntityTypeConfiguration<Student>
{
    public void Configure( EntityTypeBuilder<Student> builder )
    {
        builder.HasKey( x => x.Id );
        builder.Property( x => x.Id ).IsRequired();

        builder.Property( x => x.FirstName ).IsRequired();
        builder.Property( x => x.FamilyName ).IsRequired();
        builder.Property( x => x.BirthDate ).IsRequired();
        builder.Property( x => x.BirthPlace ).IsRequired();
        builder.Property( x => x.Gender ).IsRequired();
        builder.Property( x => x.Nationality ).IsRequired();
        builder.Property( x => x.Address ).IsRequired();
        builder.Property( x => x.DateOfRegistration ).IsRequired();
        builder.Property( x => x.AcademicYearOfRegistration ).IsRequired();
        builder.Property( x => x.StudentGuardianId ).IsRequired( false );

        builder.Property( x => x.StudyLevelId ).IsRequired();
        builder.Property( x => x.GroupId ).IsRequired();
    }
}

究竟是什么问题？

当我尝试添加新迁移时，所有这些问题都出现了这个错误

无法确定“StudentTrainingMark”类型的导航“Student.TrainingMark”表示的关系。手动配置关系，或使用“[NotMapped]”属性或使用“OnModelCreating”中的“EntityTypeBuilder.Ignore”忽略此属性。

请 - 有关如何解决此问题的任何帮助？

Answer 1

你可以设置它们的关系：

modelBuilder.Entity<StudentTrainingMark>()
            .HasOne<Student>(s => s.Student)
            .WithMany(g => g.StudentTrainingMarks)
            .HasForeignKey(s => s.StudentId);