问实体框架-实体类型之间的关联已被切断

EN

[Table("Users")]
public class UserEntity : BaseEntity
{
    [Required]
    [MaxLength(30)]
    public string Username { get; set; }
    [Required]
    [MaxLength(200)]
    public string Password { get; set; }

    [Required]
    [MaxLength(200)]
    public string Name { get; set; }

    [Required]
    [MaxLength(20)]
    public string Cellphone { get; set; }

    public virtual ICollection<UserGroupEntity> UserGroups { get; set; }


[Table("Groups")]
public class GroupEntity : BaseEntity
{
    [Required]
    [MaxLength(20)]
    public string Code { get; set; }

    [Required]
    [MaxLength(200)]
    public string Name { get; set; }
}

[Table("UserGroups")]
public class UserGroupEntity : BaseEntity
{
    [Required]
    [ForeignKey("User")]
    public int UserId { get; set; }

    [Required]
    [ForeignKey("Group")]
    public int GroupId { get; set; }

    public virtual UserEntity User { get; set; }
    public virtual GroupEntity Group { get; set; }


}

            UserEntity user = _dataContext.Users
            .Include(x => x.UserGroups)
            .ThenInclude(x => x.Group)
            .SingleOrDefault(x => x.Id == model.Id && !x.IsDeleted);


            UserGroupEntity userGroupBinding = user.UserGroups.First();
            user.UserGroups.Remove(userGroupBinding);

            _dataContext.SaveChanges();

The association between entity types 'UserEntity' and 'UserGroupEntity' has been severed but the relationship is either marked as 'Required' or is implicitly required because the foreign key is not nullable. If the dependent/child entity should be deleted when a required relationship is severed, then setup the relationship to use cascade deletes.  Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to see the key values.'

        protected override void OnModelCreating(ModelBuilder modelBuilder)
    {            
        var cascadeFKs = modelBuilder.Model.GetEntityTypes()
            .SelectMany(t => t.GetForeignKeys())
            .Where(fk => !fk.IsOwnership && fk.DeleteBehavior == DeleteBehavior.Cascade);

        foreach (var fk in cascadeFKs)
            fk.DeleteBehavior = DeleteBehavior.Restrict;



        base.OnModelCreating(modelBuilder);
    }