我有一个一对多关系,我试图在“多”方删除一组实例,但不断收到异常“不允许添加与处于已删除状态的实体的关系”。这是 Entity Framework 6.1.1。
从教师到类(class)是一对多的关系。这两个类定义为:
[Table("Course")]
public partial class Course {
public int Id { get; set; }
public int? TeacherId { get; set; }
public virtual Teacher Teacher { get; set; }
}
[Table("Teacher")]
public partial class Teacher
{
public Teacher()
{
Course = new HashSet<Course>();
}
public int Id { get; set; }
[Required]
[StringLength(50)]
public string TeacherName { get; set; }
public virtual ICollection<Course> Course { get; set; }
}
试图删除类(class)的代码是导入的一部分:一组类(class)正在传入,数据库中但不属于传入类(class)的类(class)应从数据库中删除。 (此外,应该创建属于传入集但不在数据库中的类(class),但这似乎可行)。
var existingCourses = ctx.Courses.ToList();
var toCreate = incomingCourses.Where(x => !existingCourses.Contains(x)).ToList();
var coursesToDelete = existingCourses.Where(x => !incomingCourses.Contains(x)).ToList();
ctx.Courses.RemoveRange(coursesToDelete);
ctx.SaveChanges(); // The exception occurs here
传入的类(class)集从 XML 文件解析为 DTO。在将它们与现有类(class)进行比较之前,它们被放置在一个列表中:
var incomingCourses = incomingDtos.Select(x => new Course
{
Teacher = new Teacher { TeacherName = x.TeacherNameFromXml }
}.ToList();
Course 实体上还有其他属性可标识类(class),但我没有在此处显示它们,因为我认为它们无关紧要。
调试时,我注意到正在删除的类(class)的 Teacher 属性在调用 RemoveRange()
之前是非空的,但之后是 null ..所以似乎有某种发生级联删除。
我试图通过我的 DbContext 删除所有级联删除,并在那里指定关系。这没有任何改变。
public class MyDbContext : DbContext {
public MyDbContext() {}
public MyDbContext(string connectionString) {
Database.Connection.ConnectionString = connectionString;
}
public virtual DbSet<Teacher> Teacher { get; set; }
public virtual DbSet<Course> Courses { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
modelBuilder.Entity<Teacher>()
.HasMany(x => x.Course)
.WithOptional(x => x.Teacher)
.HasForeignKey(x => x.TeacherId)
.WillCascadeOnDelete(false);
}
}
最佳答案
@LukasKabrt 的评论为我指明了正确的方向。我没有直接比较 Course 对象,而是在 LINQ 中“临时”将现有类(class)转换为 DTO 并比较 DTO。现在我可以从 coursesToDelete
var coursesToDelete = (
from e in existing
let dto = new CourseDto(e)
where !incomingDtos.Contains(dto)
select e).ToList();
关于c# - 尝试删除"Adding a relationship with an entity which is in the Deleted state is not allowed"set in optional relationship时出现"many",我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/33693066/