static void GroupJoin2()
{
var racers = Formula1.GetChampionships()
.SelectMany(cs => new List <RacerInfo>()
{
new RacerInfo
{
Year = cs.Year,
Position = 1,
FirstName = cs.First.FirstName(),
LastName = cs.First.LastName()
},
new RacerInfo
{
Year = cs.Year,
Position = 2,
FirstName = cs.Second.FirstName(),
LastName = cs.Second.LastName()
},
new RacerInfo
{
Year = cs.Year,
Position = 3,
FirstName = cs.Third.FirstName(),
LastName = cs.Third.LastName()
}
});
var q = (from r in Formula1.GetChampions()
join r2 in racers on
new
{
FirstName = r.FirstName,
LastName = r.LastName
}
equals
new
{
FirstName = r2.FirstName,
LastName = r2.LastName
}
into yearResults
select new
{
FirstName = r.FirstName,
LastName = r.LastName,
Wins = r.Wins,
Starts = r.Starts,
Results = yearResults
});
foreach (var r in q)
{
Console.WriteLine("{0} {1}", r.FirstName, r.LastName);
foreach (var results in r.Results)
{
Console.WriteLine("{0} {1}", results.Year, results.Position);
}
}
}
static void ZipOperation()
{
var racerNames = from r in Formula1.GetChampions()
where r.Country == "Italy"
orderby r.Wins descending
select new
{
Name = r.FirstName + " " + r.LastName
};
var racerNamesAndStarts = from r in Formula1.GetChampions()
where r.Country == "Italy"
orderby r.Wins descending
select new
{
LastName = r.LastName,
Starts = r.Starts
};
var racers = racerNames.Zip(racerNamesAndStarts, (first, second) => first.Name + ", starts: " + second.Starts);
foreach (var r in racers)
{
Console.WriteLine(r);
}
}
static void GroupingWithNestedObjects()
{
var countries = from r in Formula1.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(),
Racers = from r1 in g
orderby r1.LastName
select r1.FirstName + " " + r1.LastName
};
foreach (var item in countries)
{
Console.WriteLine("{0, -10} {1}", item.Country, item.Count);
foreach (var name in item.Racers)
{
Console.Write("{0}; ", name);
}
Console.WriteLine();
}
}
// 使用 Linq 函数实现 Innerjoin
// 结果 与 InnerJoin() 相同
static void InnerJoinMethod()
{
// 表内交叉
var racers = Formula1.GetChampions().
SelectMany(r => r.Years, (r, y) => new { reacer = r, year = y });
// 表内交叉
var teams = Formula1.GetContructorChampions().
SelectMany(t => t.Years, (t, y) => new { team = t, year = y });
// 两个结果再交叉
var racersAndTeams = racers.Join(teams,
r => r.year,
t => t.year,
(r, t) => new {
Year = r.year,
Champion = r.reacer.FirstName,
Constructor = t.team.Name
}).
OrderBy(y => y.Year).
Take(10);
foreach (var item in racersAndTeams)
{
Console.WriteLine("{0}: {1,-20} {2}",
item.Year, item.Champion, item.Constructor);
}
}
private static void Conversion()
{
//// query executed immediately
//List<Racer> racers = (from r in Formula1.GetChampions()
// where r.Starts > 150
// orderby r.Starts descending
// select r).ToList();
//foreach (var racer in racers)
//{
// Console.WriteLine("{0} {0:S}", racer);
//}
ILookup <string, Racer> racers = (from r in Formula1.GetChampions()
from c in r.Cars
select new
{
Car = c,
Racer = r
}).ToLookup(cr => cr.Car, cr => cr.Racer);
if (racers.Contains("Williams"))
{
foreach (var williamsRacer in racers["Williams"])
{
Console.WriteLine(williamsRacer);
}
}
}
private static void CombineRacers()
{
var q = from r in Formula1.GetChampions()
join r2 in Formula1.GetChampionships().GetRacerInfo() on
new
{
FirstName = r.FirstName,
LastName = r.LastName
}
equals
new
{
FirstName = r2.FirstName,
LastName = r2.LastName
}
into yearResults
select new
{
FirstName = r.FirstName,
LastName = r.LastName,
Wins = r.Wins,
Starts = r.Starts,
Results = yearResults
};
foreach (var item in q)
{
Console.WriteLine("{0} {1}", item.FirstName, item.LastName);
foreach (var item2 in item.Results)
{
Console.WriteLine("{0} {1}", item2.Year, item2.Position);
}
}
}
private static void SimpleFilteringWithIndex()
{
var racers = Formula1.GetChampions().Where((r, index) => r.LastName.StartsWith("A") && index % 2 != 0);
foreach (var r in racers)
{
Console.WriteLine("{0:A}", r);
}
}
private static void Sorting()
{
var racers = (from r in Formula1.GetChampions()
orderby r.Country, r.LastName, r.FirstName
select r).Take(10);
foreach (var racer in racers)
{
Console.WriteLine("{0}: {1}, {2}", racer.Country, racer.LastName, racer.FirstName);
}
}
static void Filtering()
{
var racers = from r in Formula1.GetChampions()
where r.Wins > 15 && (r.Country == "Brazil" || r.Country == "Austria")
select r;
foreach (var r in racers)
{
Console.WriteLine("{0:A}", r);
}
}
static void LINQQuery()
{
var query = from r in Formula1.GetChampions()
where r.Country == "Brazil"
orderby r.Wins descending
select r;
foreach (var r in query)
{
Console.WriteLine("{0:A}", r);
}
}
private static void LinqQuery()
{
List <Racer> champions = new List <Racer>(Formula1.GetChampions());
var query = from r in Formula1.GetChampions()
where r.Country == "Brazil"
orderby r.Wins descending
select r;
foreach (Racer r in query)
{
Console.WriteLine("{0:A}", r);
}
}
private static void LambdaExpressions()
{
List <Racer> champions = new List <Racer>(Formula1.GetChampions());
IEnumerable <Racer> brazilChampions = champions.
Where(r => r.Country == "Brazil").
OrderByDescending(r => r.Wins).
Select(r => r);
foreach (Racer r in brazilChampions)
{
Console.WriteLine("{0:A}", r);
}
}
// 多个 from 子句实现交叉表查询
// 如果筛选结果里面有集合, 就可以使用 from 进一步筛选
static void CompoundFrom()
{
var ferrariDrivers = from r in Formula1.GetChampions()
from c in r.Cars // 相当于交叉表一样, 如果 Cars 有多个 Ferrari, 结果就会重复出现几次
where c == "Ferrari" || c == "Lotus"
// orderby r.LastName
select r.FirstName + " " + r.LastName + " - " + c;
foreach (var racer in ferrariDrivers)
{
Console.WriteLine(racer);
}
}
static void CompoundFrom()
{
var ferrariDrivers = from r in Formula1.GetChampions()
from c in r.Cars
where c == "Ferrari"
orderby r.LastName
select r.FirstName + " " + r.LastName;
foreach (var racer in ferrariDrivers)
{
Console.WriteLine(racer);
}
}
static void Untyped()
{
var list = new System.Collections.ArrayList(Formula1.GetChampions() as System.Collections.ICollection);
var query = from r in list.Cast <Racer>()
where r.Country == "USA"
orderby r.Wins descending
select r;
foreach (var racer in query)
{
Console.WriteLine("{0:A}", racer);
}
}
static void SetOperations()
{
Func <string, IEnumerable <Racer> > racersByCar =
car => from r in Formula1.GetChampions()
from c in r.Cars
where c == car
orderby r.LastName
select r;
Console.WriteLine("World champion with Ferrari and McLaren");
foreach (var racer in racersByCar("Ferrari").Intersect(racersByCar("McLaren")))
{
Console.WriteLine(racer);
}
}
private static void SimpleFiltering()
{
var racers = from r in Formula1.GetChampions()
where r.Wins > 15 && (r.Country == "Brazil" || r.Country == "Austria")
select r;
var racers2 = Formula1.GetChampions().
Where(r => r.Wins > 15 && (r.Country == "Brazil" || r.Country == "Austria")).
Select(r => r);
foreach (var r in racers2)
{
Console.WriteLine("{0:A}", r);
}
}
// Cast 转换对象类型
static void Untyped()
{
var list = new System.Collections.ArrayList(Formula1.GetChampions() as System.Collections.ICollection);
// cast 将只能以 [index] 访问的集合转换成 .propertyName 的形式, 这样才可以用 foreach 遍历
var query = from r in list.Cast <Racer>()
where r.Country == "USA"
orderby r.Wins descending
select r;
foreach (var racer in query)
{
Console.WriteLine("{0:A}", racer);
}
}
private static void QuantifiersCount()
{
var racers = from r in Formula1.GetChampions()
where r.Years.Count() >= 3
orderby r.Years.Count() descending
select new
{
Name = r.FirstName + " " + r.LastName,
TimesChampion = r.Years.Count()
};
foreach (var r in racers)
{
Console.WriteLine("{0} {1}", r.Name, r.TimesChampion);
}
}
static void Aggregate()
{
var query = from r in Formula1.GetChampions()
where r.Years.Count() > 3
orderby r.Years.Count() descending
select new
{
Name = r.FirstName + " " + r.LastName,
TimesChampion = r.Years.Count()
};
foreach (var r in query)
{
Console.WriteLine("{0} {1}", r.Name, r.TimesChampion);
}
}
static void Grouping()
{
var countries = from r in Formula1.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 countries)
{
Console.WriteLine("{0, -10} {1}", item.Country, item.Count);
}
}
private static void Ordering()
{
//var racers = (from r in Formula1.GetChampions()
// orderby r.Country, r.LastName, r.FirstName
// select r).Take(10);
var racers = Formula1.GetChampions().
OrderBy(r => r.Country).
ThenBy(r => r.LastName).
ThenBy(r => r.FirstName).
Take(10);
foreach (var racer in racers)
{
Console.WriteLine("{0:C}: {0:L}, {0:F}", racer);
}
}
/* 结果与 下面的 GroupJoin2() 函数相同
*/
static void GroupJoinLinq()
{
var racers = from cs in Formula1.GetChampionships()
select new { Year = cs.Year, Numbers = new List <string>()
{
cs.First, cs.Second, cs.Third
} } into temp
from r in temp.Numbers
select new { Year = temp.Year, FirstName = r.FirstName(), LastName = r.LastName(), Position = temp.Numbers.IndexOf(r) + 1 };
var q = (from r in Formula1.GetChampions() // 只有冠军
join r2 in racers on
// 临时匿名对象
new
{
FirstName = r.FirstName,
LastName = r.LastName
}
equals
new
{
FirstName = r2.FirstName,
LastName = r2.LastName
}
into yearResults
select new
{
FirstName = r.FirstName,
LastName = r.LastName,
Wins = r.Wins,
Starts = r.Starts,
Results = yearResults
});
foreach (var r in q)
{
Console.WriteLine("{0} {1}", r.FirstName, r.LastName);
foreach (var results in r.Results)
{
Console.WriteLine("{0} {1}", results.Year, results.Position);
}
}
}
private static void GroupingAndAggregation()
{
var countries = from c in
from r in Formula1.GetChampions()
group r by r.Country into g
select new
{
Country = g.Key,
Wins = (from x in g
select x.Wins).Sum()
}
orderby c.Wins descending
select c;
foreach (var item in countries)
{
Console.WriteLine(item);
}
}
static void Aggregate2()
{
var countries = (from c in
from r in Formula1.GetChampions()
group r by r.Country into c
select new
{
Country = c.Key,
Wins = (from r1 in c
select r1.Wins).Sum()
}
orderby c.Wins descending, c.Country
select c).Take(5);
foreach (var country in countries)
{
Console.WriteLine("{0} {1}", country.Country, country.Wins);
}
}
private static void Grouping()
{
var countries = from r in Formula1.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() };
//var query = Formula1.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 countries)
{
Console.WriteLine("{0,-10} {1}", item.Country, item.Count);
}
}
static void GroupJoin()
{
// var q =
//from c in categories
//join p in products on c equals p.Category into ps
//select new { Category = c, Products = ps };
var racers = from r in Formula1.GetChampions()
from y in r.Years
select new
{
Year = y,
Name = r.FirstName + " " + r.LastName
};
var teams = from t in Formula1.GetContructorChampions()
from y in t.Years
select new
{
Year = y,
Name = t.Name
};
var racersAndTeams =
from r in racers
join t in teams on r.Year equals t.Year into ts
select new
{
Year = r.Year,
Racer = r.Name,
Constructor = ts
};
foreach (var r in racersAndTeams)
{
Console.WriteLine("{0} {1}", r.Year, r.Racer);
foreach (var t in r.Constructor)
{
Console.WriteLine("\t{0}", t.Name);
}
}
}
private static void Except()
{
var racers = Formula1.GetChampionships().SelectMany(cs => new List <RacerInfo>()
{
new RacerInfo {
Year = cs.Year,
Position = 1,
FirstName = cs.First.FirstName(),
LastName = cs.First.LastName()
},
new RacerInfo {
Year = cs.Year,
Position = 2,
FirstName = cs.Second.FirstName(),
LastName = cs.Second.LastName()
},
new RacerInfo {
Year = cs.Year,
Position = 3,
FirstName = cs.Third.FirstName(),
LastName = cs.Third.LastName()
}
});
var nonChampions = racers.Select(r =>
new
{
FirstName = r.FirstName,
LastName = r.LastName
}).Except(Formula1.GetChampions().Select(r =>
new
{
FirstName = r.FirstName,
LastName = r.LastName
}));
foreach (var r in nonChampions)
{
Console.WriteLine("{0} {1}", r.FirstName, r.LastName);
}
}
private static void TraditionalQuery()
{
List <Racer> champions = new List <Racer>(Formula1.GetChampions());
List <Racer> brazilChampions = champions.FindAll(
delegate(Racer r)
{
return(r.Country == "Brazil");
});
brazilChampions.Sort(
delegate(Racer r1, Racer r2)
{
return(r2.Wins.CompareTo(r1.Wins));
});
foreach (Racer r in brazilChampions)
{
Console.WriteLine("{0:A}", r);
}
}
private static void Partitioning()
{
int pageSize = 5;
int numberPages = (int)Math.Ceiling(Formula1.GetChampions().Count() / (double)pageSize);
for (int page = 0; page < numberPages; page++)
{
Console.WriteLine("Page {0}", page);
var racers = (from r in Formula1.GetChampions()
orderby r.LastName
select r.FirstName + " " + r.LastName).Skip(page * pageSize).Take(pageSize);
foreach (var name in racers)
{
Console.WriteLine(name);
}
Console.WriteLine();
}
}