Question

我正在尝试使用EF 7保存对象但是当我尝试更新它时，我的外键值（导航属性）会丢失。运行下面的代码后，外键在数据库中都为空。

 UserTask s = new UserTask()
        {
            Id = 10027,
            Description ="test change",
            Title = "Test change",
            DueDate = DateTime.Now.AddHours(3),
            CreatedBy = db.Users.Where(c=>c.UserName=="Bob").First(),
            AssignedTo = db.Users.Where(c => c.UserName == "Stephen").First(),
            Status = stat
        };

        db.UserTasks.Attach(s);

        db.Entry(s).State = EntityState.Modified;
        db.SaveChanges();

Answer 1

您没有在变量＆＃34; s＆＃34;中设置FK，例如s.Fk1Id，因此该字段将为null。首先从EF获取实例：

var s = db.UserTasks.Where(o=>o.Id=="10027").First();

s.Id = 10027;
s.Description ="test change";
s.Title = "Test change";
s.DueDate = DateTime.Now.AddHours(3);
s.CreatedBy = db.Users.Where(c=>c.UserName=="Bob").First();
s.AssignedTo = db.Users.Where(c => c.UserName == "Stephen").First();

更新实体时导航属性会丢失

1 个答案: