直接上代码，内容很浅显易懂，在这里就不做更多的解释，解释见代码注释。
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using
System;
using
System.Collections.Generic;
using
System.Linq;
using
System.Web;
using
System.Web.UI;
using
System.Web.UI.WebControls;
using
System.Threading.Tasks;
public
partial
class
test : System.Web.UI.Page
{ protected
void
Page_Load(object
sender, EventArgs e)
{
string[] names = { "Wang", "Biao", "WangBiao", "Kingtiger"
};
var
q1 = names.Where(a => a.StartsWith("W"));//直接查询
var
q2 = from
a in
names
where
a.StartsWith("W")
select
a;//linq查询
var
q3 = from
a in
names
where
a.StartsWith("W")
orderby
a descending
select
a;//linq查询，包括排序,倒序要加上descending
var
q4 = names.OrderBy(a => a).Where(a=>a.StartsWith("W"));//直接排序
var
q5 = names.OrderByDescending(a => a).Where(a=>a.StartsWith("W"));//直接倒序排序
var
q6 = from
a in
names
select
new
{
HI = a + ",您好！"
};//查询后重构输出
var
q7 = names.Select(a => new
{ HI = a + ",您好！"
});//直接查询构造输出
List<Person> persons = new
List<Person>();
persons.Add(new
Person() { ID="0001",Name="Kingtiger"
});
persons.Add(new
Person() { ID = "0002", Name = "Wang"
});
persons.Add(new
Person() { ID = "0001", Name = "Biao"
});
persons.Add(new
Person() { ID = "0004", Name = "WangBiao"
});
var
q8 = from
p in
persons
orderby
p.ID, p.Name
select
p;//多级排序，先排序ID，然后再排序Name
var
q9 = persons.OrderBy(a => a.ID).ThenBy(a => a.Name).Select(a => a);//直接两个排序
var
qt = from
p in
persons
where
p.Name.Contains("W") || p.Name.Contains("Biao")
select
p;//第一次查询进行过滤
var
q10 = from
p in
qt
orderby
p.Name descending
select
p.Name;//对一次查询结果进行第二次处理
var
q11 = from
p in
persons
group
p by
p.ID into
cg
select
new
{
GroupID = cg.Key,
GroupCount= cg.Count()
};//分组查询，将结果提取出来
List<Order> orders = new
List<Order>();
orders.Add(new
Order() { UserID="0002",OrderID="001", OrderName="苹果"
});
orders.Add(new
Order() { UserID = "0002", OrderID = "003", OrderName = "香蕉"
});
orders.Add(new
Order() { UserID = "0004", OrderID = "002", OrderName = "荔枝"
});
var
q12 = from
p in
persons
join
o in
orders on
p.ID equals
o.UserID
select
new
{
PName = p.Name,
POrderName = o.OrderName
};
foreach
(var
p in
q12)
{
Response.Write(p+"<br/>");
}
}
}public
class
Person
{ public
string
ID { set; get; }
public
string
Name { set; get; }
}public
class
Order
{ public
string
OrderID { set; get; }
public
string
OrderName { set; get; }
public
string
UserID { set; get; }
} |