C# Linq
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace LinqExam
{
class Program
{
static void Main(string[] args)
{
//LinqQuery();
//ExtentionMethods();
//DeferredQuery();
//WhereFunc();
//WhereIndexFunc();
//WhereTypeFunc();
//CompoundFromFunc();
//OrderbyLinqFunc();
//OrderbyExtentionFunc();
//GroupLinqFunc();
//GroupExtentionFunc();
//JoinLinqFunc();
//IntersectFunc();
//ZipFunc();
//PageFunc();
//CountFunc();
SumFunc();
Console.Read();
}
static void LinqQuery()
{
var query = from r in Formula.GetChampions()
where r.Country == "Brazil"
orderby r.Wins descending
select r;
foreach (var r in query)
{
Console.WriteLine("{0:A}", r);
}
}
static void ExtentionMethods()
{
var champions = Formula.GetChampions();
IEnumerable<Racer> brazilChampions =
champions.Where(r => r.Country == "Brazil").
OrderByDescending(r=>r.Wins).
Select(r => r);
foreach (var r in brazilChampions)
{
Console.WriteLine("{0:A}", r);
}
}
static void DeferredQuery()
{
var names = new List<string> { "Nino", "Alberto", "Juan", "Mike", "Phil" };
var namesWithJ = from n in names
where n.StartsWith("J")
orderby n
select n;
Console.WriteLine("First iteration");
foreach (string name in namesWithJ)
{
Console.WriteLine(name);
}
Console.WriteLine();
names.Add("John");
names.Add("Jim");
names.Add("Jack");
names.Add("Denny");
Console.WriteLine("Second iteration");
foreach (string name in namesWithJ)
{
Console.WriteLine(name);
}
}
//筛选
static void WhereFunc()
{
var champions = Formula.GetChampions();
var query = champions.Where(r=>r.Wins>15&&(r.Country=="Brazil" ||r.Country=="Austria"));
foreach (var r in query)
{
Console.WriteLine("{0:A}", r);
}
}
//索引筛选
static void WhereIndexFunc()
{
var query = Formula.GetChampions().Where((r, index) => r.LastName.StartsWith("A") && index % 2 != 0);
foreach (var r in query)
{
Console.WriteLine("{0:A}", r);
}
}
//类型筛选
static void WhereTypeFunc()
{
object[] data = { "abc", 123, "ggg" };
var query = data.OfType<string>();
foreach (var r in query)
{
Console.WriteLine(r);
}
}
//复合的from语句
static void CompoundFromFunc()
{
var query = from r in Formula.GetChampions()
from c in r.Cars
where c == "Ferrari"
select r.FirstName + " " + r.LastName;
foreach (var s in query)
{
Console.WriteLine(s);
}
}
//排序 linq写法
static void OrderbyLinqFunc()
{
var query = (from r in Formula.GetChampions()
orderby r.Country, r.LastName, r.FirstName
select r).Take(10);
foreach (var r in query)
{
Console.WriteLine("{0:A}", r);
}
}
//排序 扩展写法
static void OrderbyExtentionFunc()
{
var query = Formula.GetChampions()
.OrderBy(r => r.Country)
.ThenBy(r => r.LastName)
.ThenBy(r => r.FirstName)
.Select(r => r).Take(10);
foreach (var r in query)
{
Console.WriteLine("{0:A}", r);
}
}
//分组 linq写法
static void GroupLinqFunc()
{
var query = from r in Formula.GetChampions()
group r by r.Country into g
orderby g.Count() descending, g.Key
where g.Count() >= 2
select
new
{
Country = g.Key,
Count = g.Count()
};
foreach (var item in query)
{
Console.WriteLine("{0:-10} {1}",item.Country,item.Count);
}
}
//分组 扩展写法
static void GroupExtentionFunc()
{
var query = Formula.GetChampions()
.GroupBy(r => r.Country)
.OrderByDescending(g => g.Count())
.ThenBy(g => g.Key)
.Where(g => g.Count() >= 2)
.Select(g => new { Country = g.Key, Count = g.Count() });
foreach (var item in query)
{
Console.WriteLine("{0:-10} {1}", item.Country, item.Count);
}
}
//连接 linq写法
static void JoinLinqFunc()
{
var racers = from r in Formula.GetChampions()
from y in r.Years
where y > 2003
select
new
{
Year = y,
Name = r.FirstName + " " + r.LastName
};
var teams = from t in Formula.GetContructorChampions()
from y in t.Years
where y > 2003
select
new
{
Year = y,
Name = t.Name
};
var racersAndTeams = from r in racers
join t in teams on r.Year equals t.Year
select
new
{
Year = r.Year,
Racer = r.Name,
Team = t.Name
};
foreach (var item in racersAndTeams)
{
Console.WriteLine(item);
}
}
//集合Intersect Union Distinct Except
static Func<string, IEnumerable<Racer>> racersByCar =
car => from r in Formula.GetChampions()
from c in r.Cars
where c == car
orderby r.LastName
select r;
static void IntersectFunc()
{
var query = racersByCar("Ferrari").Intersect(racersByCar("McLaren"));
foreach (var item in query)
{
Console.WriteLine(item);
}
}
//合并
static void ZipFunc()
{
var racerNames = from r in Formula.GetChampions()
where r.Country == "Italy"
orderby r.Wins descending
select
new
{
Name = r.FirstName + " " + r.LastName
};
var racerNameAndStarts = from r in Formula.GetChampions()
where r.Country == "Italy"
orderby r.Wins descending
select
new
{
Name = r.LastName,
Starts = r.Starts
};
var racers = racerNames.Zip(racerNameAndStarts,
(first, second) => first.Name + ",Starts:" + second.Starts);
foreach (var item in racers)
{
Console.WriteLine(item);
}
}
//分区
static void PageFunc()
{
int pageSize = 5;
int pageCount = (int)Math.Ceiling(Formula.GetChampions().Count / (double)pageSize);
for (int i = 0; i < pageCount; i++)
{
Console.WriteLine("Page " + i.ToString());
var racers = (from r in Formula.GetChampions()
orderby r.LastName
select r.FirstName + " " + r.LastName).Skip(i * pageSize).Take(pageSize);
foreach (var item in racers)
{
Console.WriteLine(item);
}
}
}
//聚合 Count Sum Min Max Average Aggregate
static void CountFunc()
{
var racers = from r in Formula.GetChampions()
where r.Years.Count() > 2
orderby r.Years.Count() descending
select
new
{
Name = r.FirstName + " " + r.LastName,
TimesChampion = r.Years.Count()
};
foreach (var item in racers)
{
Console.WriteLine(item);
}
}
static void SumFunc()
{
var Countries =
(
from c in
(
from r in Formula.GetChampions()
group r by r.Country into g
select
new
{
Country = g.Key,
wins = (from r1 in g select r1.Wins).Sum()
}
)
orderby c.wins descending, c.Country
select c
).Take(5);
foreach (var item in Countries)
{
Console.WriteLine(item);
}
}
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ClassLibrary
{
[Serializable]
public class Racer:IComparable<Racer>,IFormattable
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string Country { get; set; }
public int Wins { get; set; }
public int Starts { get; set; }
public string[] Cars { get; private set; }
public int[] Years { get; private set; }
public Racer(string firstName = null, string lastName = null, string country = null, int starts = 0, int wins = 0, IEnumerable<int> years = null, IEnumerable<string> cars = null)
{
this.FirstName = firstName;
this.LastName = lastName;
this.Country = country;
this.Starts = starts;
this.Wins = wins;
var yearsList = new List<int>();
foreach (var year in years)
{
yearsList.Add(year);
}
this.Years = yearsList.ToArray();
var carList = new List<string>();
foreach (var car in cars)
{
carList.Add(car);
}
this.Cars = carList.ToArray();
}
public int CompareTo(Racer other)
{
if (other == null) throw new ArgumentNullException("other");
return this.LastName.CompareTo(other.LastName);
}
public string ToString(string format, IFormatProvider formatProvider)
{
switch (format)
{
case null:
case "N":
return ToString();
case "F":
return FirstName;
case "L":
return LastName;
case "C":
return Country;
case "S":
return Starts.ToString();
case "W":
return Wins.ToString();
case "A":
return String.Format("{0} {1}, {2}; starts: {3}, wins: {4}",
FirstName, LastName, Country, Starts, Wins);
default:
throw new FormatException(String.Format("Format {0} not supported", format));
}
}
public override string ToString()
{
return String.Format("{0} {1}", FirstName, LastName);
}
public string ToString(string format)
{
return ToString(format, null);
}
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ClassLibrary
{
[Serializable]
public class Team
{
public Team(string name, params int[] years)
{
this.Name = name;
this.Years = years;
}
public string Name { get; private set; }
public int[] Years { get; private set; }
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ClassLibrary
{
public static class Formula
{
private static List<Racer> racers;
public static IList<Racer> GetChampions()
{
if (racers == null)
{
racers = new List<Racer>(40);
racers.Add(new Racer("Nino", "Farina", "Italy", 33, 5, new int[] { 1950 }, new string[] { "Alfa Romeo" }));
racers.Add(new Racer("Alberto", "Ascari", "Italy", 32, 10, new int[] { 1952, 1953 }, new string[] { "Ferrari" }));
racers.Add(new Racer("Juan Manuel", "Fangio", "Argentina", 51, 24, new int[] { 1951, 1954, 1955, 1956, 1957 }, new string[] { "Alfa Romeo", "Maserati", "Mercedes", "Ferrari" }));
racers.Add(new Racer("Mike", "Hawthorn", "UK", 45, 3, new int[] { 1958 }, new string[] { "Ferrari" }));
racers.Add(new Racer("Phil", "Hill", "USA", 48, 3, new int[] { 1961 }, new string[] { "Ferrari" }));
racers.Add(new Racer("John", "Surtees", "UK", 111, 6, new int[] { 1964 }, new string[] { "Ferrari" }));
racers.Add(new Racer("Jim", "Clark", "UK", 72, 25, new int[] { 1963, 1965 }, new string[] { "Lotus" }));
racers.Add(new Racer("Jack", "Brabham", "Australia", 125, 14, new int[] { 1959, 1960, 1966 }, new string[] { "Cooper", "Brabham" }));
racers.Add(new Racer("Denny", "Hulme", "New Zealand", 112, 8, new int[] { 1967 }, new string[] { "Brabham" }));
racers.Add(new Racer("Graham", "Hill", "UK", 176, 14, new int[] { 1962, 1968 }, new string[] { "BRM", "Lotus" }));
racers.Add(new Racer("Jochen", "Rindt", "Austria", 60, 6, new int[] { 1970 }, new string[] { "Lotus" }));
racers.Add(new Racer("Jackie", "Stewart", "UK", 99, 27, new int[] { 1969, 1971, 1973 }, new string[] { "Matra", "Tyrrell" }));
racers.Add(new Racer("Emerson", "Fittipaldi", "Brazil", 143, 14, new int[] { 1972, 1974 }, new string[] { "Lotus", "McLaren" }));
racers.Add(new Racer("James", "Hunt", "UK", 91, 10, new int[] { 1976 }, new string[] { "McLaren" }));
racers.Add(new Racer("Mario", "Andretti", "USA", 128, 12, new int[] { 1978 }, new string[] { "Lotus" }));
racers.Add(new Racer("Jody", "Scheckter", "South Africa", 112, 10, new int[] { 1979 }, new string[] { "Ferrari" }));
racers.Add(new Racer("Alan", "Jones", "Australia", 115, 12, new int[] { 1980 }, new string[] { "Williams" }));
racers.Add(new Racer("Keke", "Rosberg", "Finland", 114, 5, new int[] { 1982 }, new string[] { "Williams" }));
racers.Add(new Racer("Niki", "Lauda", "Austria", 173, 25, new int[] { 1975, 1977, 1984 }, new string[] { "Ferrari", "McLaren" }));
racers.Add(new Racer("Nelson", "Piquet", "Brazil", 204, 23, new int[] { 1981, 1983, 1987 }, new string[] { "Brabham", "Williams" }));
racers.Add(new Racer("Ayrton", "Senna", "Brazil", 161, 41, new int[] { 1988, 1990, 1991 }, new string[] { "McLaren" }));
racers.Add(new Racer("Nigel", "Mansell", "UK", 187, 31, new int[] { 1992 }, new string[] { "Williams" }));
racers.Add(new Racer("Alain", "Prost", "France", 197, 51, new int[] { 1985, 1986, 1989, 1993 }, new string[] { "McLaren", "Williams" }));
racers.Add(new Racer("Damon", "Hill", "UK", 114, 22, new int[] { 1996 }, new string[] { "Williams" }));
racers.Add(new Racer("Jacques", "Villeneuve", "Canada", 165, 11, new int[] { 1997 }, new string[] { "Williams" }));
racers.Add(new Racer("Mika", "Hakkinen", "Finland", 160, 20, new int[] { 1998, 1999 }, new string[] { "McLaren" }));
racers.Add(new Racer("Michael", "Schumacher", "Germany", 250, 91, new int[] { 1994, 1995, 2000, 2001, 2002, 2003, 2004 }, new string[] { "Benetton", "Ferrari" }));
racers.Add(new Racer("Fernando", "Alonso", "Spain", 132, 21, new int[] { 2005, 2006 }, new string[] { "Renault" }));
racers.Add(new Racer("Kimi", "Räikkönen", "Finland", 148, 17, new int[] { 2007 }, new string[] { "Ferrari" }));
racers.Add(new Racer("Lewis", "Hamilton", "UK", 44, 9, new int[] { 2008 }, new string[] { "McLaren" }));
}
return racers;
}
private static List<Team> teams;
public static IList<Team> GetContructorChampions()
{
if (teams == null)
{
teams = new List<Team>()
{
new Team("Vanwall", 1958),
new Team("Cooper", 1959, 1960),
new Team("Ferrari", 1961, 1964, 1975, 1976, 1977, 1979, 1982, 1983, 1999, 2000, 2001, 2002, 2003, 2004, 2007, 2008),
new Team("BRM", 1962),
new Team("Lotus", 1963, 1965, 1968, 1970, 1972, 1973, 1978),
new Team("Brabham", 1966, 1967),
new Team("Matra", 1969),
new Team("Tyrrell", 1971),
new Team("McLaren", 1974, 1984, 1985, 1988, 1989, 1990, 1991, 1998),
new Team("Williams", 1980, 1981, 1986, 1987, 1992, 1993, 1994, 1996, 1997),
new Team("Benetton", 1995),
new Team("Renault", 2005, 2006 )
};
}
return teams;
}
}
}
