EFCore 数据播种缺失数据插入？

如何解决EFCore 数据播种缺失数据插入？

我有两个相关的类如下：

public class Student
{
    public long Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
    public long FavoriteCourseId { get; set; }
}

public class Course
{
    public long Id { get; set; }
    public string Name { get; set; }
}

两者之间是一对一的关系。 Student 有一个外键，它通过 Course 引用 FavoriteCourseId。

我的流畅映射如下：

protected override void OnModelCreating(ModelBuilder modelBuilder) {
  modelBuilder.Entity<Student>(entity => {
    entity.ToTable("Student").HasKey(k => k.Id);
    entity.Property(p => p.Id).HasColumnName("StudentID");
    entity.Property(p => p.Name).Isrequired();
    entity.Property(p => p.Email).Isrequired();
    entity.Property(p => p.FavoriteCourseId).Isrequired();
  });

  modelBuilder.Entity<Course>(entity => {
    entity.ToTable("Course").HasKey(k => k.Id);
    entity.Property(p => p.Id).HasColumnName("CourseID");
    entity.Property(p => p.Name).Isrequired();
  });

  modelBuilder.Entity<Student>()
            .HasOne(typeof(Course))
            .WithOne()
            .HasForeignKey("Student","FavoriteCourseId")
            .HasConstraintName("FK_Student_Course");

  modelBuilder.Entity<Course>().HasData(
            new Course { Id = 1,Name = "Calculus" },new Course { Id = 2,Name = "Chemistry" },new Course { Id = 3,Name = "Literature" },new Course { Id = 4,Name = "Trigonometry" },new Course { Id = 5,Name = "Microeconomics" });

  modelBuilder.Entity<Student>().HasData(
     new Student { Id = 1,Name = "Alice",Email = "[e-mail]",FavoriteCourseId = 2 },new Student { Id = 2,Name = "Bob",Email = "[e-mail]",FavoriteCourseId = 2 });
}

在这里，我正在播种两个学生 - Alice 和 Bob。但是，当我创建 init 迁移时，迁移的种子只有 Bob，而忽略 Alice。

migrationBuilder.InsertData(
            table: "Student",columns: new[] { "StudentID","Email","FavoriteCourseId","Name" },values: new object[] { 2L,"[e-mail]",2L,"Bob" });

为什么 Alice 的数据行被忽略了？我还注意到只有当 Alice 和 Bob 的 FavoriteCourseId 相同时，数据行才会被忽略。如果我将两行的 FavoriteCourseId 更改为不同的值，则会插入 Alice。

解决方法

它只播种一名学生，因为根据您的模型，同一门课程只能有一名学生。把模型改成这样：

public class Student
{
   [Key]
    public long Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
    public long FavoriteCourseId { get; set; }
    [ForeignKey(nameof(FavoriteCourseId ))]
     [InverseProperty("FavoriteCourses")]
      public virtual Course FavoriteCourse { get; set; }
}

public class Course
{
    [Key]
    public long Id { get; set; }
    public string Name { get; set; }
    [InverseProperty(nameof(Student.FavoriteCourse))]
    public virtual ICollection<Student> Students{ get; set; }
}

和 dbcontext:

modelBuilder.Entity<Student>(entity =>
{
 entity.HasOne(d => d.FavoriteCourse)
 .WithMany(p => p.Courses)
 .HasForeignKey(d => d.FavoriteCourseId)
  .OnDelete(DeleteBehavior.ClientSetNull);
}

modelBuilder.Entity<Course>().HasData(
            new Course { Id = 1,Name = "Calculus" },new Course { Id = 2,Name = "Chemistry" },new Course { Id = 3,Name = "Literature" },new Course { Id = 4,Name = "Trigonometry" },new Course { Id = 5,Name = "Microeconomics" });

  modelBuilder.Entity<Student>().HasData(
     new Student { Id = 1,Name = "Alice",Email = "[e-mail]",FavoriteCourseId = 2 },new Student { Id = 2,Name = "Bob",Email = "[e-mail]",FavoriteCourseId = 2 });