c# EF框架的增删改查操作

查询

        /// <summary>/// 查询/// </summary>private void SQLLoad(){//linq查询，方法一//var UserInfoList = from u in db.UserInfo//给个变量u，用来接收查询结果对象//select u;//查询结果对象 //db.UserInfo.Find(1);//依据主键查询,方法二//依据条件查询，如果数据返回类型是IQueryable说明是延迟查询,方法三//var UserInfoList = db.UserInfo.Where(u => u.ID > 0);//这里还没有开始查询//查询所有,方法四(不是延迟查询)  var UserInfoList = db.UserInfo.ToList();List<UserInfo> list = new List<UserInfo>();foreach (var userInfo in UserInfoList){list.Add(userInfo);}dgv.DataSource = list;}

追加

        /// <summary>/// 追加/// </summary>private void Add(){UserInfo userInfo = new UserInfo{UName = "heidashuai",UPwd = "123",SubTime = DateTime.Now,DelFlag = 0,ModifiedOn = DateTime.Now,Remark = "皮蛋",Sort = "21"};//db.UserInfo.Add(userInfo);db.Entry<UserInfo>(userInfo).State = System.Data.Entity.EntityState.Added;db.SaveChanges();}

修改

        private void AQLUpdate(){#region 官方推荐--修改已改变的//UserInfo userInfo = db.UserInfo.Where(u => u.ID == 1).FirstOrDefault();//返回            的是UserInfo的代理类（包装类）//userInfo.UPwd = "8888";//到这一步时，包装类会给真实的类修改属性，并且会给他状态谁这位已修改状态//db.SaveChanges();查询//SQLLoad();#endregion#region 方式二--修改所有数据UserInfo userInfo = db.UserInfo.Where(u => u.ID == 1).FirstOrDefault();userInfo.Remark = "自律的人真帅！";db.Entry<UserInfo>(userInfo).State = System.Data.Entity.EntityState.Modified;db.SaveChanges();SQLLoad();#endregion}

删除

        /// <summary>/// 删除/// </summary>private void SQLDelete(){UserInfo userInfo = new UserInfo { ID = 21 };//也可以从数据库查询到//方式一//db.UserInfo.Attach(userInfo);//db.UserInfo.Remove(userInfo);//方式二//告诉上下文对此实体进行跟新操作db.Entry(userInfo).State = System.Data.Entity.EntityState.Deleted;//告诉上下文把实体的变化保存到数据库里面去db.SaveChanges();}

分页查询

        /// <summary>/// 分页查询/// </summary>private void Paging(){int pageIndex = 0;int pageSize = 0;if (txtIndex.Text != "" && txtSIze.Text != ""){pageIndex = Convert.ToInt32(txtIndex.Text);pageSize = Convert.ToInt32(txtSIze.Text);}if (pageIndex <= 0 && pageSize <= 0){pageIndex = 1;pageSize = 5;txtIndex.Text = pageIndex.ToString();txtSIze.Text = pageSize.ToString();}//分页查询一一定要排序var userInfo = db.UserInfo.OrderBy(u => u.ID).Skip((pageIndex - 1) * pageSize).Take(pageSize).ToList();List<UserInfo> list = new List<UserInfo>();foreach (var item in userInfo){list.Add(item);}dgv.DataSource = list;}