public void Select()
{
HuNiEntities huni = new HuNiEntities();
//基于表达式的查询语法
using (var edm = new HuNiEntities())
{
string esql = "select value c from NorthwindEntities.Customers as c order by c.CustomerID limit 10";
//ObjectQuery<Teacher> objectQuery = edm.CreateQuery<Teacher>(esql);
ObjectContext context = new ObjectContext("sql");
ObjectQuery <Teacher> customers = new ObjectQuery <Teacher>(esql, context);
IQueryable <Teacher> cust1 = from c in customers select c;
//使用ObjectQuery类的ToTraceString()方法显示查询SQL语句
customers.ToTraceString();
}
using (var edm = new EmptyModelContainer())
{
Teacher teacher = edm.Set <Teacher>().Find(3);
Student arti = teacher.Student.ToList().Find(o => o.ID == 2);
//取当前值
DbPropertyValues currentValues = edm.Entry <Teacher>(teacher).CurrentValues;
//取原值
DbPropertyValues originalValues = edm.Entry <Teacher>(teacher).OriginalValues;
//取数据库值
DbPropertyValues databaseValues = edm.Entry <Teacher>(teacher).GetDatabaseValues();
}
}
//IQueryable<T> 是将Skip ,take 这些方法表达式翻译成T-SQL语句之后再向SQL服务器发送命令，它并不是把所有数据都加载到内存里来才进行条件过滤
//IEnumerable<T> 泛型类在调用自己的SKip 和 Take 等扩展方法之前数据就已经加载在本地内存里了，
public void test()
{
using (HuNiEntities _HuNiEntities = new HuNiEntities())
{
//查询的结果放入IQueryable接口的集合中
IQueryable <Base_Area> classesIQue = (from c in _HuNiEntities.Base_Area orderby c.ID select c).Skip <Base_Area>(3).Take <Base_Area>(3);
//注意这个AsEnumerable<T_Class>()在分页查询之前，先将其转换成IEnumerable类型
IEnumerable <Base_Area> classesIEnu = (from c in _HuNiEntities.Base_Area orderby c.ID select c).AsEnumerable <Base_Area>().Skip <Base_Area>(3).Take <Base_Area>(3);
}
}
