private static void SelectMany2()
{
// flatten the year list to return a list of all racers and positions in the championship
var racers = Formula1.GetChampionships()
.SelectMany(cs => new List <dynamic>()
{
new {
Year = cs.Year,
Position = 1,
Name = cs.First
},
new {
Year = cs.Year,
Position = 2,
Name = cs.Second
},
new {
Year = cs.Year,
Position = 3,
Name = cs.Third
}
});
foreach (var s in racers)
{
Console.WriteLine(s);
}
}
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);
}
}
}
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);
}
}
}
// 筛选多个结果
private static void SelectMany2()
{
var racers = Formula1.GetChampionships()
.Where(r => r.Year > 2000)
.SelectMany(cs => new List <dynamic>() // dynamic 是定义弱对象
// 自定义对象的属性名
// 然后用 cs 数据赋值;
// 将原数据经过封装后, 生成匿名对象返回
{
new {
Year = cs.Year,
Position = 1,
Name = cs.First,
xx = "hello kitty"
} /*,
* new {
* Year = cs.Year,
* Position = 2,
* Name = cs.Second
* }*/
});
foreach (var s in racers)
{
Console.WriteLine(s);
}
}
/* 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 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);
}
}
/*
* 根据名字列表和 年份123名次, 求出每个名字在<哪年>获得<第几名>
*/
static void GroupJoin2()
{
var racers = Formula1.GetChampionships() // 年份+123名
/* 把年份 * 1,2,3名 交叉,
*
* 将 1950 first second third
* 形成如下格式:
* year pos name
* ------------------------------------------
* 1950 1 first(firstname, lastname)
* 1950 2 second(firstname, lastname)
* 1950 3 third(firstname, lastname)
*
* 然后用名字列表, 即冠军列表中的名字列表与上表中的 name 作为join 的key
*/
.SelectMany(cs => new List <RacerInfo>()
{
// 封装年份 + 123名次
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() // 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);
}
}
}