C# LINQ学习笔记二：LINQ标准查询操作概述

class Program
{
static void Main(string[] args)
{
#region LINQ Select
var words = new[] { "the", "quick", "brown", "fox", "jumps" };
var query =
from word in words
select word.Substring(, );
foreach (var word in query)
{
Console.WriteLine(word);
}
Console.Read();
#endregion
}
}

class Program
{
static void Main(string[] args)
{
#region LINQ SelectMany
var phrases = new List<string>() { "an apple a day", "the quick brown fox" };
var query =
from phrase in phrases
from word in phrase.Split(' ')
select word;
foreach (var word in query)
{
Console.WriteLine(word);
}
Console.Read();
#endregion
}
}

/// <summary>
/// 花束类
/// </summary>
class Bouquet
{
public List<string> Flowers { get; set; }
} class Program
{
static void Main(string[] args)
{
#region LINQ Select和SelectMany比较
var bouquets = new List<Bouquet>()
{
new Bouquet {Flowers = new List<string> {"sunflower", "daisy", "daffodil", "larkspur"}},
new Bouquet {Flowers = new List<string> {"tulip", "rose", "orchid"}},
new Bouquet {Flowers = new List<string> {"gladiolis", "lily", "snapdragon", "aster", "protea"}},
new Bouquet {Flowers = new List<string> {"larkspur", "lilac", "iris", "dahlia"}}
}; IEnumerable<List<string>> query1 = bouquets.Select(bq => bq.Flowers);
IEnumerable<string> query2 = bouquets.SelectMany(bq => bq.Flowers); Console.WriteLine("query1->Select():");
foreach (IEnumerable<string> collection in query1)
{
foreach (var item in collection)
{
Console.WriteLine(item);
}
} Console.WriteLine("\nquery2->SelectMany():");
foreach (var item in query2)
{
Console.WriteLine(item);
} Console.Read();
#endregion
}
}

class Program
{
static void Main(string[] args)
{
#region LINQ 分组数据
var numbers = new List<int>() { , , , , , , , , , };
IEnumerable<IGrouping<bool, int>> query = from number in numbers
group number by number % == ;
foreach (var group in query)
{
Console.WriteLine($"{(group.Key ? "偶数" : "基数")}：");
foreach (var item in group)
{
Console.WriteLine(item);
}
}
Console.Read();
#endregion
}
}

/// <summary>
/// 植物类
/// </summary>
class Plant
{
public string Name { get; set; }
} /// <summary>
/// 食肉植物类
/// </summary>
class CarnivorousPlant : Plant
{
public string TrapType { get; set; }
} class Program
{
static void Main(string[] args)
{
#region LINQ 转换数据类型
var plants = new Plant[]
{
new CarnivorousPlant {Name = "Venus Fly Trap", TrapType = "Snap Trap"},
new CarnivorousPlant {Name = "Pitcher Plant", TrapType = "Pitfall Trap"},
new CarnivorousPlant {Name = "Sundew", TrapType = "Flypaper Trap"},
new CarnivorousPlant {Name = "Waterwheel Plant", TrapType = "Snap Trap"}
};
var query = from CarnivorousPlant plant in plants
where plant.TrapType == "Snap Trap"
select plant;
foreach (var carnivorousPlant in query)
{
Console.WriteLine(carnivorousPlant.Name);
}
Console.Read();
#endregion
}
}