我有两个 Entity Framework 实体。 1) 员工 2) 案例
我在 Entity Framework Core 中为多对多关系建模。
我可以像这样添加关系:
[HttpPost]
public async Task<Employee> AddCaseEmployee([FromBody]EmployeeCase employeeCase)
{
Case lcase = await _caseGenericService.GetSingleIncludingAsync(employeeCase.CaseId);
lcase.EmployeeCases = new List<EmployeeCase>();
lcase.EmployeeCases.Add(new EmployeeCase
{
CaseId = employeeCase.CaseId,
EmployeeId = employeeCase.EmployeeId
}
);
await _caseGenericService.UpdateAsync(lcase);
Employee employee = await _employeeGenericService.GetSingleIncludingAsync(employeeCase.EmployeeId);
return employee;
}
现在我正在尝试删除这样的关系之一:
[HttpDelete]
public async Task<Employee> DeleteCaseEmployee(long employeeId, long caseId)
{
Case lcase = await _caseGenericService.GetSingleIncludingAsync(caseId,
a => a.EmployeeCases);
//lcase.EmployeeCases.Remove(new EmployeeCase
//{
// CaseId = caseId,
// EmployeeId = employeeId
//}
//);
EmployeeCase employeeCase =
lcase.EmployeeCases.FirstOrDefault(ec => ec.EmployeeId == employeeId && ec.CaseId == caseId);
lcase.EmployeeCases.Remove(employeeCase);
try
{
await _caseGenericService.UpdateAsync(lcase);
}
catch(Exception ex)
{
}
Employee employee = await _employeeGenericService.GetSingleIncludingAsync(employeeId);
return employee;
}
你可以看到我的第一次尝试被注释掉了。 所以我尝试了第二种方法,只是取回我要删除的记录的引用,将其从集合中删除,然后调用 update.但我得到这个错误:
“实体类型'Case'和'EmployeeCase'之间的关联已被切断,但此关系的外键不能设置为null。 如果要删除依赖实体,则设置关系以使用级联删除。"
这里我不需要删除案例或员工。我只需要删除加入记录。 进入该记录的唯一方法是从案例或员工进入关系。
如果我将 EmployeeCase 对象设为 Dbset,则模型将不会构建。
这是我建立的 OnModelBuilding 关系:
modelBuilder.Entity<EmployeeCase>()
.HasKey(ec => new { ec.EmployeeId, ec.CaseId });
modelBuilder.Entity<EmployeeCase>()
.HasOne(ec => ec.Employee)
.WithMany(e => e.EmployeeCases)
.HasForeignKey(ec => ec.EmployeeId);
modelBuilder.Entity<EmployeeCase>()
.HasOne(ec => ec.Case)
.WithMany(c => c.EmployeeCases)
.HasForeignKey(ec => ec.CaseId);
// Get rid of Cascading Delete Circular references error.
var type = modelBuilder.Model.GetEntityTypes().Single(t => t.Name == "Hrsa.Core.Generic.Model.Lerd.EmployeeCase");
foreach (var relationship in type.GetForeignKeys())
{
relationship.DeleteBehavior = DeleteBehavior.Restrict;
}
我必须关闭连接对象 EmployeeCase 的删除,它不能是 DbSet。如果不遵循其中任何一个步骤,多对多模型将无法构建。
我需要做的就是能够删除这条记录。我不需要删除员工或案例。
这里是 POCO。
public class Employee : BaseEntity
{
[BindNever]
public string Email { get; set; }
[BindNever]
public long OrganizationId { get; set; }
[BindNever]
public string Supervisor { get; set; }
[BindNever]
public string SupervisorEmail { get; set; }
[BindNever]
public string FirstName { get; set; }
[BindNever]
public string LastName { get; set; }
public string Notes { get; set; }
[BindNever]
public long BargainingUnitId { get; set; }
[BindNever]
public long PayPlanId { get; set; }
[BindNever]
public long GradeRankId { get; set; }
[BindNever]
public long PositionTitleId { get; set; }
[BindNever]
public long SeriesId { get; set; }
public bool IsUnionEmployee { get; set; }
public virtual Organization Organization { get; set; }
public virtual BargainingUnit BargainingUnit { get; set; }
public virtual PayPlan PayPlan { get; set; }
public virtual GradeRank GradeRank { get; set; }
public virtual PositionTitle PositionTitle { get; set; }
public virtual Series Series { get; set; }
public virtual ICollection<UnionHours> UnionHours { get; set; }
[NotMapped]
public string UnionEmployeeYesNo => (IsUnionEmployee) ? "Yes" : "No";
public virtual ICollection<EmployeeCase> EmployeeCases { get; set; }
}
public class Case : BaseEntity
{
#region Common Case Properties
public long InitialContactId { get; set; }
public virtual Employee InitialContact { get; set; }
[DataType(DataType.Date)]
public DateTime? InitialConsultDate { get; set; }
public string LerSpecialistId { get; set; }
public virtual AppUser LerSpecialist { get; set; }
public string Notes { get; set; }
public bool IsDeleted { get; set; }
public CaseType CaseType { get; set; }
#endregion
#region EmployeeCase Properties
//public long PrimaryEmployeeId { get; set; }
//public virtual Employee PrimaryEmployee {get;set;}
public virtual ICollection<EmployeeCase> EmployeeCases { get; set; }
#endregion
#region NonEmployeeCase Properties
//public long PrimaryNonEmployeeId { get; set; }
//public virtual Employee PrimaryEmployee {get;set;}
public virtual ICollection<NonEmployeeCase> NonEmployeeCases { get; set; }
#endregion
}
和连接表(同样,它不是 DbSet,但就添加关系而言,一切都在工作。现在无法删除。)
public class EmployeeCase
{
[ForeignKey("Id")]
public long EmployeeId { get; set; }
public Employee Employee { get; set; }
[ForeignKey("Id")]
public long CaseId { get; set; }
public Case Case { get; set; }
}
我怎样才能删除这个多对多关系记录?
最佳答案
我遇到了同样的需求,并在这里找到了这篇文章。由于尚未发布真正的解决方案(使用 EF),因此我决定添加此答案:
另见 Updating many to many relationships in Entity Framework Core ;那是为了更新,但同样的原则也适用于删除。
这是我的代码(我的场景是用户 N↔N 组):
var groupToUpdate = _userGroupsContext.Groups.Include(g => g.UserGroups).Single(u => u.Id == userVm.groupsIds[0]);
var userToUpdate = _userGroupsContext.Users.Single(u => u.Id == userVm.user.Id);
groupToUpdate.UserGroups.Remove(groupToUpdate.UserGroups.Where(ugu => ugu.UserId == userToUpdate.Id).FirstOrDefault());
_userGroupsContext.SaveChanges();
UserGroups
字段是包含 group
的中间类(表)的列表。和 groupId
, user
和 userId
属性。
关于many-to-many - 如何删除 Entity Framework Core 中的多对多关系?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43481552/