linq復習
9998 ワード
/// <summary>
/// join
/// </summary>
public void Test6()
{
var namelist = new[] {
new{id = "1", name = "Jon"},
new{id = "2", name = "Holly"},
new{id = "1", name = "Tom"},
new{id = "3", name = "Tom"},
new{id = "3", name = "Tom"}
};
var dtlist = new[] {
new{id = "2", age = 23, },
new{id = "2", age = 28, },
new{id = "3", age = 26},
new{id = "1", age = 25}
};
var query = from n in namelist
join d in dtlist
on n.id equals d.id into tempdt
select new
{
};
//...
}
/// <summary>
///
/// </summary>
public void Test8()
{
// ， ，
//var q = from e1 in db.Employees
// from e2 in e1.Employees
// where e1.City == e2.City
// select new
// {
// name1 = e1.FirstName + e1.LastName,
// name2 = e2.FirstName + e2.LastName,
// e1.City
// };
}
/// <summary>
/// => (Two way join)
/// </summary>
///
public void Test9()
{
//var q = from c in db.Customers
// join o in db.Orders on c.CustomerID
// equals o.CustomerID into orders
// select new
// {
// c.ContactName,
// OrderCount = orders.Count()
// };
/* ， 1， c（from c in db.Customers），
* Many， o ( join o in db.Orders )，
* c， o， o， orders， ，
* o orders， into 。 select ，orders Count。
*/
}
/// <summary>
/// join
/// </summary>
public void Test5()
{
var str = new[] {
new{id = "1", name = "Jon"},
new{id = "2", name = "Holly"},
new{id = "3", name = "Tom"}
};
var str2 = new[] {
new{id = "2", age = 23},
new{id = "3", age = 26},
new{id = "1", age = 25}
};
var query = from n in str
join a in str2
on n.id equals a.id into tempa
from ta in tempa.DefaultIfEmpty()
select new
{
n,
ta
};
foreach (var item in query)
{
Response.Write(string.Format("name:{0}, age:{1}<br />", item.n.name, item.ta.age.ToString()));
/*
name:Jon, age:25
name:Holly, age:23
name:Tom, age:26
*/
}
//
//var categories = from p in db.Products
// group p by p.CategoryID into g
// select new
// {
// CategoryID = g.Key,
// CheapestProducts = from p2 in g
// where p2.UnitPrice == g.Min(x => x.UnitPrice)
// //
// //where p2.UnitPrice == g.Average(x = x.UnitPrice)
// select p2
// };
}
/// <summary>
/// join、
/// </summary>
public void Test4()
{
//
// var str = new { id = "1", name = "jon" };
//
var str = new[] {
new{id = "1", name = "Jon"},
new{id = "2", name = "Holly"},
new{id = "3", name = "Tom"}
};
var str2 = new[] {
new{id = "1", name = "Robin"},
new{id = "2", name = "William"},
new{id = "2", name = "kkk"},
new{id = "3", name = "jjjj"}
};
//
//var query = from a in str
// join b in str2 on a.id equals b.id
// select new { Aname = a.name, Bname = b.name };
//foreach (var item in query)
//{
// Response.Write(string.Format("Aname:{0}, Bname:{1}", item.Aname, item.Bname) + "<br />");
// /*
// Aname:Jon, Bname:Robin
// Aname:Holly, Bname:William
// Aname:Holly, Bname:kkk
// Aname:Tom, Bname:jjjj
// */
//}
var query = from a in str
join b in str2 on a.id equals b.id into temp2
select new
{
a,
temp2
};
foreach (var item in query)
{
Response.Write(string.Format("Aname:{0}, =>Bname Count:{1}", item.a.name, item.temp2.Count()) + "<br />");
/*
Aname:Jon, =>Bname Count:1
Aname:Holly, =>Bname Count:2
Aname:Tom, =>Bname Count:1
*/
}
}
/// <summary>
/// group by
/// </summary>
public void Test3()
{
char[] gitem = { 'a', 'b', 'c', 'f' }; //
string[] str = { "aa", "bb", "cc", "dd", "fine" };
//var query = from s in str
// group s by s[0] into ws // s， s[0]
// where gitem.Contains(ws.Key)
// orderby ws.Key ascending
// select ws.Key;
var q = from s in str
where gitem.Contains(s[0])
select s;
//foreach (var item in query)
foreach (var item in q)
{
//Response.Write(string.Format("{0},<br />", item));
/*
a,
b,
c,
f,
*/
Response.Write(string.Format("{0},<br />", item));
}
}
/// <summary>
/// let
/// </summary>
public void Test2()
{
string[] strings = { "A penny saved is a penny earned.", "The aaxly sdj", "the pa is no" };
// a e ，
var g = from j in strings
let w = j.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries)
from k in w
let nw = k.ToLower()
where nw[0] == 'a' || nw[0] == 'e'
select k;
foreach (var item in g)
{
Response.Write(string.Format("{0},<br />", item));
}
}
/// <summary>
///
/// </summary>
public void Test1()
{
List<Student> students = new List<Student>
{
new Student
{
LastName="xiaogui",Scores=new List<int>{97,42,91,60}
},
new Student
{
LastName="xiaozhan",Scores=new List<int>{50,92,81,60}
},
new Student
{
LastName="xiaolan",Scores=new List<int>{32,32,81,90}
},
new Student
{
LastName="xiaowan",Scores=new List<int>{92,22,81,60}
},
};
// 90
var q = from s in students
from o in s.Scores
where o > 90
select new
{
lastname = s.LastName,
o
};
foreach (var item in q)
{
Response.Write(string.Format("{0}:{1}<br />", item.lastname, item.o));
/*Note：xiaogui 2
*
xiaogui:97
xiaogui:91
xiaozhan:92
xiaowan:92
*/
}
}
}//testlinq
public class Student
{
public string LastName { get; set; }
public List<int> Scores { get; set; }
}
public class Employee
{
public string First { get; set; }
public string Last { get; set; }
public int ID { get; set; }
}