具有相同键的对象已存在于ObjectStateManager中

Question

无法将多对多属性保存到数据库。

错误详情：

具有相同键的对象已存在于ObjectStateManager中。 ObjectStateManager无法使用相同的键跟踪多个对象。

我试图在此操作方法中保存属性：

       [HttpPost]
        public ActionResult Edit(UserRole role)
        {
            var permissionNameList=  (from per in _db.Permissions
                                               select per.Name).Distinct().ToList();
            foreach(var name in permissionNameList)
            {
                role.Permissions.Add(new permission(name, oper));
            }

            if (ModelState.IsValid)
            {
                _db.Entry(role).State = System.Data.EntityState.Modified;
                _db.SaveChanges();
                return RedirectToAction("Index");
            }
            return View(role);
        }

数据库表结构是这样的：

3桌

userRole permissionsInRoles userRole permission

CREATE TABLE newsmonitoringmanagement.permission
(
Id          INT NOT NULL auto_increment,
Name        VARCHAR (50) NOT NULL,
Description VARCHAR (250) NULL,
Operations  INT NOT NULL,
PRIMARY KEY (Id),
UNIQUE KEY UK_permissionIdentity (Name, Operations)
);

在db-context中：

        modelBuilder.Entity<UserRole>()
            .HasMany(usrRole => usrRole.Permissions)
            .WithMany(permisn => permisn.Roles)
            .Map(m =>
            {
                m.ToTable("permissionsInRoles");
                m.MapLeftKey("RoleId");
                m.MapRightKey("PermissionId");
            });

        modelBuilder.Entity<Permission>()
            .HasMany(per => per.Roles)
            .WithMany(role => role.Permissions)
            .Map(m =>
            {
                m.ToTable("permissionsInRoles");
                m.MapLeftKey("PermissionId");
                m.MapRightKey("RoleId");
            });

---

更新后，此处的新代码可以使用，但似乎已连接，因为arg role的permissions属性为empty

var permissionNameList = (from per in _db.Permissions
                                  select per.Name).Distinct().ToList();
        var realRole = (from r in _db.UserRoles
                        where r.Id == role.Id
                        select r).First();

        foreach (var perm in realRole.Permissions)
        {
            var opert = Convert.ToInt32(Request.Form[perm.Name + "_op"]);
            if (perm.Name.InList(permissionNameList))
            {
                perm.Operations = opert;
            }
        }

        if (ModelState.IsValid)
        {
            _db.Entry(realRole).State = System.Data.EntityState.Modified;
            _db.SaveChanges();
        }

Answer 1

name field是权限表中的唯一字段吗？
如果是，那么显然您不能授予与先前name相同的新权限，这就是您正在做的事情。
编辑：-您不能只添加从数据库中获取的权限
我的意思是确实真的有必要创建新的权限
像这样的东西

var permissionList=  (from per in _db.Permissions
                                               select per).Distinct();

            foreach(var permission in permissionList)
            {

                var opert = Convert.ToInt32(Request.Form[name + "_op"]);
                //var per=new Permission();
                //per.Name=name;
                permmission.Operations=opert;
                role.Permissions.Add(permission);
            }

Answer 2

从数据库中检索的modefy代码然后工作。

public ActionResult Edit(UserRole role)
{
    var permissionNameList = (from per in _db.Permissions
                              select per.Name).Distinct().ToList();
    var realRole = (from r in _db.UserRoles
                    where r.Id == role.Id
                    select r).First();

    foreach (var perm in realRole.Permissions)
    {
        var opert = Convert.ToInt32(Request.Form[perm.Name + "_op"]);
        if (perm.Name.InList(permissionNameList))
        {
            perm.Operations = opert;
        }
    }

    if (ModelState.IsValid)
    {
        _db.Entry(realRole).State = System.Data.EntityState.Modified;
        _db.SaveChanges();
    }

    this.TempData["msg"] = "[EditRolePermissions]Saved Role Id " + role.Id;
    return RedirectToAction("Details/" + role.Id);
}