LINQ小实用的Demo，在学无止境的路上，每天一点小进步，知识才会累积成多嘛。
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Fun LQIN to Object");
QueryOverStrings();
QueryOverInts();
IEnumerable<string> subset = GetSttringSubset();
foreach (var item in subset)
{
Console.WriteLine(item);
}
foreach (var item in GetStringSubsetArray())
{
Console.WriteLine(item);
}
Console.WriteLine("***********LINQ over Generic collections***************");
List<Car> myCars = new List<Car>()
{
new Car{ PetName="Henry",Color="Silver",Speed=100,Mack="BMW"},
new Car{ PetName="Daisy",Color="Tan",Speed=90,Mack="BMW"},
new Car{ PetName="Mary",Color="Black",Speed=55,Mack="VW"},
new Car{ PetName="Clunker",Color="Rust",Speed=5,Mack="Yugo"},
new Car{ PetName="Melvin",Color="White",Speed=43,Mack="Ford"},
};
GetFastCars(myCars);
GetFastBMWs(myCars);
LINQOverArrayList();
OfTypeAsFilter();
ProductInfo[] itemInSrock = new[]
{
new ProductInfo{Name="Mac' s Coffee",Description="Coffee with TEETH",NumberInStock=24},
new ProductInfo{Name="Milk Maid Milk",Description="Milk cow's love",NumberInStock=100},
new ProductInfo{Name="Pure Silk Tofu",Description="Bland as Possible",NumberInStock=120},
new ProductInfo{Name="Cruchy Pops",Description="Cheezy,peppery goodness",NumberInStock=2},
new ProductInfo{Name="RipOff water",Description="From the tap to your wallet",NumberInStock=100},
new ProductInfo{Name="Classic Valpo pizza!",Description="Everyone loves pizza",NumberInStock=73},
};
SelectEverything(itemInSrock);
ListProductNames(itemInSrock);
GetOverstock(itemInSrock);
GetNameasDescriptions(itemInSrock);
Array obj = GetProjectedSubset(itemInSrock);
foreach (var item in obj)
{
Console.WriteLine(item.ToString());
}
GetCountFromQuery();
ReverseFromQuery(itemInSrock);
DispalyConcatNoDups();
AvggregateOps();
QueryStringWithEnumberableAndLambdas();
Console.ReadLine();
}
#region LINQ
/// <summary>
/// 将LINQ查询应用于原始数组
/// </summary>
static void QueryOverStrings()
{
string[] currentVideoGames = { "Morrowind", "Uncharted 2", "Fallout 3", "Daxter", "System Shock 2" };
IEnumerable<string> subset = from g in currentVideoGames
where g.Contains(" ")
orderby g
select g;
foreach (var item in subset)
{
Console.WriteLine("Item:{0}", item);
}
}
/// <summary>
/// LINQ和隐式类型本地变量
/// </summary>
static void QueryOverInts()
{
int[] number = { 10, 20, 30, 40, 1, 2, 3, 9 };
IEnumerable<int> subset = from i in number
where i < 10
select i;
foreach (var item in subset)
{
Console.WriteLine("Item:{0}", item);
}
}
/// <summary>
/// 立即执行的作用，并返回Int的数组和集合
/// </summary>
static void ImmediateExecution()
{
int[] number = { 10, 20, 30, 40, 1, 2, 3, 9 };
//立即获取数据为int[]
int[] subsetIntArray = (from i in number where i < 10 select i).ToArray<int>();
//立即获取数据为List<Int>
List<int> subsetAsListArray = (from i in number where i < 10 select i).ToList<int>();
}
/// <summary>
/// 使用IEnumberable,返回LINQ查询的结果
/// </summary>
/// <returns></returns>
static IEnumerable<string> GetSttringSubset()
{
string[] colors = { "Light Red", "Green", "Yellow", "Dark Red", "Red", "Purple" };
//注意,subset是Ienumberable<string>兼容的对象
IEnumerable<string> theRedColor = from c in colors
where c.Contains("Red")
select c;
return theRedColor;
}
/// <summary>
/// 通过立即执行返回LINQ结果，返回toArray 数组类型
/// </summary>
/// <returns></returns>
static string[] GetStringSubsetArray()
{
string[] colors = { "Light Red", "Green", "Yellow", "Dark Red", "Red", "Purple" };
var theRedColor = from i in colors
where i.Contains("Red")
select i;
//将结果映射为数组
return theRedColor.ToArray();
}
/// <summary>
/// 访问包含的子对象,抓取Speed属性大于55的项
/// </summary>
/// <param name="myCars"></param>
static void GetFastCars(List<Car> myCars)
{
var fastCars = from c in myCars where c.Speed > 55 select c;
foreach (var item in fastCars)
{
Console.WriteLine("{0} is going too fast!", item.PetName);
}
}
/// <summary>
/// 抓取Speed属性大于90的宝马车
/// </summary>
/// <param name="myCars"></param>
static void GetFastBMWs(List<Car> myCars)
{
var fastCars = from c in myCars where c.Speed > 90 && c.Mack == "BMW" select c;
foreach (var item in fastCars)
{
Console.WriteLine("{0} is going too fast!", item.PetName);
}
}
/// <summary>
/// 将LINQ查询应用于非泛型集合
/// </summary>
static void LINQOverArrayList()
{
Console.WriteLine("***********LINQ over ArrayList************");
ArrayList myCars = new ArrayList()
{
new Car{ PetName="Henry",Color="Silver",Speed=100,Mack="BMW"},
new Car{ PetName="Daisy",Color="Tan",Speed=90,Mack="BMW"},
new Car{ PetName="Mary",Color="Black",Speed=55,Mack="VW"},
new Car{ PetName="Clunker",Color="Rust",Speed=5,Mack="Yugo"},
new Car{ PetName="Melvin",Color="White",Speed=43,Mack="Ford"},
};
//把arrayList转换为一个兼容于IENumberable<T>类型
var myCarsEnum = myCars.OfType<Car>();
var fastCars = from c in myCarsEnum where c.Speed > 55 select c;
foreach (var item in fastCars)
{
Console.WriteLine("{0} is going too fast!", item.PetName);
}
}
/// <summary>
/// 使用OfType<T>筛选数据，<T> 是返回数据的类型 OfType<Int>即集合中的Int数据，则只返回Int数据
/// </summary>
static void OfTypeAsFilter()
{
ArrayList arr = new ArrayList();
arr.AddRange(new object[] { 10, 400, 8, false, new Car(), "String data" });
var myInts = arr.OfType<int>();
foreach (var item in myInts)
{
Console.WriteLine("Int Value:{0}", item);
}
}
/// <summary>
/// 基本的选择语法
/// </summary>
/// <param name="products"></param>
static void SelectEverything(ProductInfo[] products)
{
//得到所有的对象
Console.WriteLine("All Product details");
var allProducts = from p in products select p;
foreach (var item in allProducts)
{
Console.WriteLine("Name:{0}", item);
}
}
/// <summary>
/// 使用LINQ语法只提取产品的名字
/// </summary>
/// <param name="products"></param>
static void ListProductNames(ProductInfo[] products)
{
//只获取产品的名字
Console.WriteLine("Only Product Name:");
var allProducts = from p in products select p.Name;
foreach (var item in allProducts)
{
Console.WriteLine("Name:{0}", item);
}
}
/// <summary>
/// 使用LINQ提取库存量大于25的项
/// </summary>
/// <param name="products"></param>
static void GetOverstock(ProductInfo[] products)
{
//只获取产品的名字
Console.WriteLine("the overstock item:");
var overstock = from p in products where p.NumberInStock > 25 select p;
foreach (var item in overstock)
{
Console.WriteLine(item.ToString());
}
}
/// <summary>
/// 投影新数据类型,select new {返回只需要的值}
/// </summary>
/// <param name="products"></param>
static void GetNameasDescriptions(ProductInfo[] products)
{
Console.WriteLine("Name And Descriotions:");
var nameDesc = from p in products select new { p.Name, p.Description };
foreach (var item in nameDesc)
{
Console.WriteLine(item.ToString());
}
}
/// <summary>
/// 使用ToArray()扩展方法,将查询结果转换为.NET System.Array对象 也返回select new {p.Name,p.Description}
/// </summary>
/// <param name="products"></param>
/// <returns></returns>
static Array GetProjectedSubset(ProductInfo[] products)
{
var nameDesc = from p in products select new { p.Name, p.Description };
return nameDesc.ToArray();
}
/// <summary>
/// 使用IEnumberable获取总数
/// </summary>
static void GetCountFromQuery()
{
string[] currentVideoGames = { "Morrowind", "Uncharted 2", "Fallout 3", "Daxter", "System Shock 2" };
int num = (from i in currentVideoGames where i.Length > 6 select i).Count();
Console.WriteLine("{0}Items honor the LINQ query.", num);
}
/// <summary>
/// 反转结果集
/// </summary>
/// <param name="products"></param>
static void ReverseFromQuery(ProductInfo[] products)
{
Console.WriteLine("Product in reverse");
var allProducts = from p in products select p;
foreach (var item in allProducts.Reverse())
{
Console.WriteLine(item.ToString());
}
}
/// <summary>
/// 对表达式进行排序,默认为正序，你也可以使用ascending操作符，逆序可以使用descending操作符
/// </summary>
/// <param name="products"></param>
static void AlPhabetizeProductNames(ProductInfo[] products)
{
//按字母排序获取产品的名称
var allProducts = from p in products orderby p.Name select p;
Console.WriteLine("orderby name");
foreach (var item in allProducts.Reverse())
{
Console.WriteLine(item.ToString());
}
}
/// <summary>
/// 移除重复值
/// </summary>
static void DispalyConcatNoDups()
{
List<string> myCars = new List<string>() { "Yugo", "Aztec", "BMW" };
List<string> yourCars = new List<string>() { "BMW", "Saab", "Aztec" };
var carConcat = (from c in myCars select c).Concat(from c1 in yourCars select c1);
foreach (var item in carConcat.Distinct())
Console.WriteLine(item);
}
/// <summary>
/// 不同的聚合函数（max、min、avg、sum）
/// </summary>
static void AvggregateOps()
{
double[] temps = { 2.0, -21.3, 8, -4, 0, 8.2 };
//不同的聚合函数
Console.WriteLine("MAX:{0}",(from c in temps select c).Max());
Console.WriteLine("Min:{0}", (from c in temps select c).Min());
Console.WriteLine("Average:{0}", (from c in temps select c).Average());
Console.WriteLine("Sum:{0}", (from c in temps select c).Sum());
}
/// <summary>
/// 通过Enumbetable类型赋array的扩展方法建立查询表达式
/// </summary>
static void QueryStringWithEnumberableAndLambdas()
{
string[] currentVideoGames = { "Morrowind", "Uncharted 2", "Fallout 3", "Daxter", "System Shock 2" };
//通过Enumbetable类型赋array的扩展方法建立查询表达式
var subset = currentVideoGames.Where(x => x.Contains(" ")).OrderBy(x => x).Select(x => x);
foreach (var item in subset)
Console.WriteLine("item:{0}",item);
}
#endregion
}
class Car
{
public string PetName { get; set; }
public string Color { get; set; }
public int Speed { get; set; }
public string Mack { get; set; }
}
class ProductInfo
{
public string Name { get; set; }
public string Description { get; set; }
public int NumberInStock { get; set; }
public override string ToString()
{
return string.Format("Name={0},Description={1},NumberInStock={2}", Name, Description, NumberInStock);
}
}
}