linq WHERE

1.简单形式：

var q =
from c in db.Customers
where c.City == "London"
select c;

var q =
from e in db.Employees
where e.HireDate >= new DateTime(1994, 1, 1)
select e;

2.关系条件形式：

var q =
from p in db.Products
where p.UnitsInStock <= p.ReorderLevel && !p.Discontinued
select p;

var q =
from p in db.Products
where p.UnitPrice > 10m || p.Discontinued
select p;

//这里要看看。如果实现了接口的话。就可以用了，主要是说OBJECT。

var q =
db.Products.Where(p=>p.UnitPrice > 10m).Where(p=>p.Discontinued);

3.First()形式：

返回集合中的一个元素，其实质就是在SQL语句中加TOP (1)

Shipper shipper = db.Shippers.First();

Customer cust = db.Customers.First(c => c.CustomerID == "BONAP");

Order ord = db.Orders.First(o => o.Freight > 10.00M);