EF 增删改查的内存状态详解

User userNew = new User()
{
    Account = "Admin",
    State = 0,
    CompanyId = 4,
    CompanyName = "天国集团",
    CreateTime = DateTime.Now,
    CreatorId = 1,
    Email = "[email protected]",
    LastLoginTime = null,
    LastModifierId = 0,
    LastModifyTime = DateTime.Now,
    Mobile = "13960699696",
    Name = "yoyo",
    Password = "12356789",
    UserType = 1
};
using (JDDbContext context = new JDDbContext())
{
    Console.WriteLine(context.Entry<User>(userNew).State);//实体跟context没关系 Detached
    userNew.Name = "小鱼";
    context.SaveChanges();//Detached啥事儿不发生

    context.Users.Add(userNew);
    Console.WriteLine(context.Entry<User>(userNew).State);//Added
    context.SaveChanges();//插入数据(自增主键在插入成功后，会自动赋值过去)
    Console.WriteLine(context.Entry<User>(userNew).State);//Unchanged（跟踪，但是没变化）

    userNew.Name = "加菲猫";//修改----内存clone 
    Console.WriteLine(context.Entry<User>(userNew).State);//Modified
    context.SaveChanges();//更新数据库，因为状态是Modified
    Console.WriteLine(context.Entry<User>(userNew).State);//Unchanged（跟踪，但是没变化）

    context.Users.Remove(userNew);
    Console.WriteLine(context.Entry<User>(userNew).State);//Deleted
    context.SaveChanges();//删除数据，因为状态是Deleted
    Console.WriteLine(context.Entry<User>(userNew).State);//Detached已经从内存移除了
    //user.Name = "IT小白龙";//只能更新这个字段
    //context.Entry<User>(user).State = EntityState.Modified;//全字段更新