Exemples d'utilisation d'opérations de requête C#Linq

Opérateur de requête standard Linq

Requête d'ensemble de langage Ganmge hteg.ratedQuw, LINQ, intègre des requêtes dans la syntaxe du langage de programmation C#, vous pouvez utiliser la même syntaxe pour accéder à différentes sources de données. LINQ fournit une couche d'abstraction pour différentes sources de données, afin que la même syntaxe puisse être utilisée.

1 Opérateur de filtre

L'opérateur de filtre définit les conditions de retour des éléments.

筛选操作符	描述
where	使用谓词，返回布尔值
OfType3bb63614c352f1576fbc58977cc251c2	根据类型筛选元素

Exemples d'application :
où utilisation :

 var racers = from r in Formulal.Racers                         
 where r.Wins > 15 && r.Country == "Brazil" select r;

OfType48aeceac32e3a5d1541cebb95288d598

ToList 集合转化为List ToDictionary 集合转化为Dictionary Cast3bb63614c352f1576fbc58977cc251c2 映射

还是上面的例子

         IEnumerable<MyIntClass> ienuList = from r in intList1 where r.Integar > 3 select r; //返回默认的IEnumerable集合
         List<MyIntClass> ienuList2 = (from r in intList1 where r.Integar > 3 select r).ToList(); //返回List
         MyIntClass[] ienuList2 = (from r in intList1 where r.Integar > 3 select r).ToArray();//返回数组
         var dict = (from r in intList1 where r.Integar > 3 select r).ToDictionary(r=>r.Name,r=>r.Integar); //字典，key是name, value：Integar
         IEnumerable<MyIntClass> ienuList2 = (from r in intList1 where r.Integar > 3 select r).AsEnumerable();

12生成操作符（Generation operators）

这些生成操作符返回 一 个新集合

Generation operators	描述
Empty	集合是空的
Range	返回一系列数字
Repeat	返回始终重复一个值的集合

IEnumerable<int> ints = Enumerable.Range(3, 10);
//{3,4,5,6,7,8,9,10,11,12}IEnumerable<int> emptyInts =  Enumerable.Empty<int>();
//生成一个空集合IEnumerable<int> ints2= Enumerable.Repeat(6,8);
//生成8个6的集合

附：展示所用到的实体类和数据

选手实体类

   //选手实体类
   public class Racer 
    {        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 yearList = new List<int>();            
        if (years != null)
            {                
            foreach (var year in years)
                {
                    yearList.Add(year);
                }                this.Years = yearList.ToArray();
            }            if (cars != null)
            {                var carList = new List<string>();                
            foreach (var car in cars)
                {
                    carList.Add(car);
                }                
                this.Cars = carList.ToArray();
            }           public string FirstName { get; set; }          
             public string LastName { get; set; }           //赢得比赛的次数
           public int Wins { get; set; }           //所属国家
           public string Country { get; set; }           //开始做的年龄
           public int Starts { get; set; }           //车型数组
           public string[] Cars { get; private set; }           //赢得冠军的年份
           public int[] Years { get; private set; }   
         }
      }

选手数据

//选手实体类
   public class Racer 
    {
        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 yearList = new List<int>();
            if (years != null)
            {
                foreach (var year in years)
                {
                    yearList.Add(year);
                }
                this.Years = yearList.ToArray();
            }
            if (cars != null)
            {
                var carList = new List<string>();
                foreach (var car in cars)
                {
                    carList.Add(car);
                }
                this.Cars = carList.ToArray();
            }

           public string FirstName { get; set; }
           public string LastName { get; set; }
           //赢得比赛的次数
           public int Wins { get; set; }
           //所属国家
           public string Country { get; set; }
           //开始做的年龄
           public int Starts { get; set; }
           //车型数组
           public string[] Cars { get; private set; }
           //赢得冠军的年份
           public int[] Years { get; private set; }   
         }
      }
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选手数据

//选手List
        public static List<Racer> Racers = new List<Racer>(40)
        {         
                new Racer("Nino", "Farina", "Italy", 33, 5, new int[] { 1950 }, new string[] { "Alfa Romeo" }),
                new Racer("Alberto", "Ascari", "Italy", 32, 10, new int[] { 1952, 1953 }, new string[] { "Ferrari" }),
                new Racer("Juan Manuel", "Fangio", "Argentina", 51, 24, new int[] { 1951, 1954, 1955, 1956, 1957 }, 
                new string[] { "Alfa Romeo", "Maserati", "Mercedes", "Ferrari" }),
                new Racer("Mike", "Hawthorn", "UK", 45, 3, new int[] { 1958 }, new string[] { "Ferrari" }),
                new Racer("Phil", "Hill", "USA", 48, 3, new int[] { 1961 }, new string[] { "Ferrari" }),
                new Racer("John", "Surtees", "UK", 111, 6, new int[] { 1964 }, new string[] { "Ferrari" }),
                new Racer("Jim", "Clark", "UK", 72, 25, new int[] { 1963, 1965 }, new string[] { "Lotus" }),
                new Racer("Jack", "Brabham", "Australia", 125, 14, new int[] { 1959, 1960, 1966 }, new string[] { "Cooper", "Brabham" }),
                new Racer("Denny", "Hulme", "New Zealand", 112, 8, new int[] { 1967 }, new string[] { "Brabham" }),
                new Racer("Graham", "Hill", "UK", 176, 14, new int[] { 1962, 1968 }, new string[] { "BRM", "Lotus" }),
                new Racer("Jochen", "Rindt", "Austria", 60, 6, new int[] { 1970 }, new string[] { "Lotus" }),
                new Racer("Jackie", "Stewart", "UK", 99, 27, new int[] { 1969, 1971, 1973 }, new string[] { "Matra", "Tyrrell" }),
                new Racer("Emerson", "Fittipaldi", "Brazil", 143, 14, new int[] { 1972, 1974 }, new string[] { "Lotus", "McLaren" }),
                new Racer("James", "Hunt", "UK", 91, 10, new int[] { 1976 }, new string[] { "McLaren" }),
                new Racer("Mario", "Andretti", "USA", 128, 12, new int[] { 1978 }, new string[] { "Lotus" }),
                new Racer("Jody", "Scheckter", "South Africa", 112, 10, new int[] { 1979 }, new string[] { "Ferrari" }),
                new Racer("Alan", "Jones", "Australia", 115, 12, new int[] { 1980 }, new string[] { "Williams" }),
                new Racer("Keke", "Rosberg", "Finland", 114, 5, new int[] { 1982 }, new string[] { "Williams" }),
                new Racer("Niki", "Lauda", "Austria", 173, 25, new int[] { 1975, 1977, 1984 }, new string[] { "Ferrari", "McLaren" }),
                new Racer("Nelson", "Piquet", "Brazil", 204, 23, new int[] { 1981, 1983, 1987 }, new string[] { "Brabham", "Williams" }),
                new Racer("Ayrton", "Senna", "Brazil", 161, 41, new int[] { 1988, 1990, 1991 }, new string[] { "McLaren" }),
                new Racer("Nigel", "Mansell", "UK", 187, 31, new int[] { 1992 }, new string[] { "Williams" }),
                new Racer("Alain", "Prost", "France", 197, 51, new int[] { 1985, 1986, 1989, 1993 }, new string[] { "McLaren", "Williams" }),
                new Racer("Damon", "Hill", "UK", 114, 22, new int[] { 1996 }, new string[] { "Williams" }),
                new Racer("Jacques", "Villeneuve", "Canada", 165, 11, new int[] { 1997 }, new string[] { "Williams" }),
                new Racer("Mika", "Hakkinen", "Finland", 160, 20, new int[] { 1998, 1999 }, new string[] { "McLaren" }),
                new Racer("Michael", "Schumacher", "Germany", 287, 91, new int[] { 1994, 1995, 2000, 2001, 2002, 2003, 2004 }, 
                new string[] { "Benetton", "Ferrari" }),
                new Racer("Fernando", "Alonso", "Spain", 252, 32, new int[] { 2005, 2006 }, new string[] { "Renault" }),
                new Racer("Kimi", "Räikkönen", "Finland", 230, 20, new int[] { 2007 }, new string[] { "Ferrari" }),
                new Racer("Lewis", "Hamilton", "UK", 166, 43, new int[] { 2008, 2014, 2015 }, new string[] { "McLaren", "Mercedes" }),
                new Racer("Jenson", "Button", "UK", 283, 15, new int[] { 2009 }, new string[] { "Brawn GP" }),
                new Racer("Sebastian", "Vettel", "Germany", 156, 42, new int[] { 2010, 2011, 2012, 2013 }, new string[] { "Red Bull Racing" })

        };

团队实体类

    [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; }
    }

团队数据

        //冠军团队List
        public static List<Team> ChampionTeams = 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),            
        new Team("Brawn GP", 2009),            
        new Team("Red Bull Racing", 2010, 2011, 2012, 2013),            
        new Team("Mercedes", 2014, 2015)
        };

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