Question

当我尝试删除我的教师记录时收到以下错误。

DELETE语句与REFERENCE约束冲突 “FK_dbo.Department_dbo.Teacher_TeacherID”。冲突发生在数据库“MySchoolBook”，表“dbo.Department”，列“TeacherID”。声明已经终止。

我的老师模特：

public class Teacher : Person
{
    [Key]
    public Guid TeacherID { get; set; }

    public Guid? AccountID { get; set; }

    public virtual ICollection<Classroom> Classrooms { get; set; }

    public virtual Office Office { get; set; }
}

我的部门模特：

public class Department
{
    [Key]
    public Guid DepartmentID { get; set; }

    [Display(Name = "Administrator")]
    public Guid? TeacherID { get; set; }

    [Required(ErrorMessage = "Name is required.")]
    public String Name { get; set; }

    public virtual Teacher Administrator { get; set; }
    public virtual ICollection<Classroom> Classrooms { get; set; }
}

我的DbContext：

protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();

            modelBuilder.Entity<Department>()
                .HasOptional(d => d.Administrator);
        }

编辑：

我想要发生的是当我删除我的教师记录时，我的部门的TeacherID列变为NULL。

Answer 1

我想要发生的是当我删除我的教师记录时，我的部门的TeacherID列变为NULL。

您必须手动将TeacherID设置为null。 EF不会为你做这件事：

using (var context = new MyContext())
{
    var teacher = context.Teachers
        .SingleOrDefault(t => t.TeacherID == teacherToDeleteID);

    if (teacher != null)
    {
        var departments = context.Departments
            .Where(d => d.TeacherID == teacherToDeleteID);
        foreach (var department in departments)
            department.TeacherID = null;

        context.Teachers.Remove(teacher);

        context.SaveChanges();
    }
}

修改

您可以尝试删除循环，仅将部门加载到上下文中。当您删除教师时，自动关系修正可能会将TeacherID FK设置为null，但我不确定：

using (var context = new MyContext()) { var teacher = context.Teachers .SingleOrDefault(t => t.TeacherID == teacherToDeleteID); if (teacher != null) { context.Departments.Where(d => d.TeacherID == teacherToDeleteID).Load(); context.Teachers.Remove(teacher); context.SaveChanges(); } }

EF与延迟加载。无法删除记录

1 个答案: