17.03.16 EF框架

Lambda表达式

Lambda不使用delegate关键字,而使用Lambda运算符=>

FuncgetInput = (int age) => {
  return Console.ReadLine() + age;
}

Entity Framework 实体框架--DataBaseFirst

EF添加数据

UserInfo userInfo = new UserInfo();
userInfo.UserName = "Caty";
EFFristModelEntities db = new EFFristModelEntities ();
db.UserInfo.Add(userInfo);
db.SaveChanges();

EF查询延迟加载

EFFristModelEntities db = new EFFristModelEntities ();
//linq表达式
var userInfoList = from u in db.UserInfo where u.ID == 343 select u;
// EF延迟加载机制,数据用到时才去查询
foreach (UserInfo userInfo in userInfoList)
{
  Response Write(userInfo.UserName);
}

删除数据

EFFristModelEntities db = new EFFristModelEntities ();
var userInfoList = from u in db.UserInfo where u.ID == 343 select u;
// 返回第一个元素,如果没有,返回null
UserInfo userInfo = userinfoList.FirstDefault();
if(userInfo != null)
{
  db.UserInfo.Remove(userInfo);
  //db.Entry.State = System.Data.EntityState.Deleted;
  db.SaveChanges();
}
else
{
  Resopnse.Write("要删除的数据不存在");
}

更新数据

EFFristModelEntities db = new EFFristModelEntities ();
var userInfoList = from u in db.UserInfo where u.ID == 343 select u;
UserInfo userInfo = userinfoList.FirstDefault();
userInfo.UserName = "小猫";
db.Entry.State = System.Data.EntityState.Modified;
db.SaveChanges();

EF框架--ModelFirst

导航属性应用(添加数据)

Model2Container db = new Model2Container ();
Customer customer = new Customer(){ CustomerName="张三",CustomerPwd="123" };
OrderInfo orderInfo1 = new OrderInfo(){ ID=Guid.NewGuid(),OrderNum = "10001",createDateeTime=Datetime.Now,Customer=customer };
db.Customer.Add(customer);
db.OrderInfo.Add(orderInfo1);
db.saveChanges();

查询数据

Model2Container db = new Model2Container ();
// 查询所有客户的订单
var customerList = from c in db.Customer select c;
foreach(var customer in customerList)
{
  Response.Write( customer. CustomerName+":" );
  foreach ( var orderInfo in customer.OrderInfo )  
  {
    Response.Write(orderInfo.orderNum+",");
  }
}
// 查询单个客户的订单
var customerInfoList = from c in db.Customer where c.ID == 1 select c;
var customerInfo = customerInfoList.FirstOrDefault();
foreach(var orderInfo in customerInfo.OrderInfo)
{
  Response.write(orderInfo.OrderNum);
}

EF框架-CodeFirst

/* ClassInfo.cs */
public class ClassInfo
{
  [Key] //主键
  public int Id { get; set; }
  [StringLength(32)]
  [Required] //不允许为空
  public string ClassName { get; set; }
  [Required]
  public DateTime CreateTime{ get; set; }
  public virtual ICollection StudentInfo { get; set; }
}

/* StudentInfo.cs */
public class StudentInfo
{
  [Key] //主键
  public int Id { get; set; }
  [StringLength(32)]
  [Required]
  public string StuName { get; set; }
  [Required]
  public DateTime SubTime{ get; set; }
  public virtual ClassInfo ClassInfo { get; set; }
}

/* App.config */

  
    
  


/* CodeFirstDbContext.cs */
public class CodeFirstDbContext:DbContext
{
  public CodeFirstDbContext() : base("name=connStr")
  {
  }
  protected override void OnModelCreating(DbModelBuilder modelBuilder)
  {
   //移除复数形式
   modelBuilder.conventions.Remove();
  }
 public DbSet ClassInfo { get; set; }
 public DbSet StudentInfo { get; set; }
}

查询部分列

EFFristModelEntities db = new EFFristModelEntities ();
var userInfoList = from u in db.UserInfo where u.ID == 343 select new{UName=u.UserName,UPwd=u.UserPass};
foreach (Var userInfo in userInfoList)
{
  Response Write(userInfo.UName+":"+userInfo.UPwd);
}

Lambda查询

EFFristModelEntities db = new EFFristModelEntities ();
// 升序排序, 降序排序用orderByDescending
var userInfoList = db.userInfo.where true).OrderBy(u => u.ID);
//分页 Skip(2)跳过两条记录;Take(2) 取两条记录;
int pageIndex = 2;
int pageSize = 2;
var userInfoList = db.userInfo.where true).OrderBy(u => u.ID).Skip((pageIndex-1)*pageSize).Take(pageSize);
// IQueryable userInfoList = db.userInfo.whereu.ID==343);

线程唯一

EFFirstModelEntities db = null;
if(HttpContext.Current.Items["db"] == null)
{
  db = new EFFirstModelEntities();
  HttpContext.Current.Items["db"] = db;
}
else
{
  db = HttpContext.Current.Items["db"] as EFFristModelEntities;
}