Unity学习（C#）——LINQ的使用

武林大师

 class MartialArtsMaster
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public int age { get; set; }
        public string MenPai { get; set; }
        public string KongFu { get; set; }
        public int Level { get; set; }

        public override string ToString()
        {
            return string.Format("ID:{0}, Name = :{1}, age =: {2}, MenPai = :{3}, KongFu = :{4}, Level = :{5}",ID,Name,age,MenPai,KongFu,Level);
        }
        
    }

武功类型

class Kongfu
    {
        public int ID { set; get; }
        public string Name { get; set; }
        public int Power { get; set; }
    }

class Program
    {
        static void Main(string[] args)
        {
            var mastreList = new List<MartialArtsMaster>()
            {
                new MartialArtsMaster(){ID=1,Name="岳不群",age=58,MenPai="华山",KongFu="葵花宝典",Level=10},
                new MartialArtsMaster(){ID=2,Name="风清扬",age=23,MenPai="华山",KongFu="孤独九剑",Level=7},
                new MartialArtsMaster(){ID=3,Name="梅超风",age=45,MenPai="桃花岛",KongFu="九阴真经",Level=9}
            };
            var kongfu = new List<Kongfu>()
            {
                new Kongfu(){ID=1,Name="打狗棒法",Power=90},
                new Kongfu(){ID=2,Name="降龙十八掌",Power=100},
                new Kongfu(){ID=3,Name="葵花宝典",Power=90},
                new Kongfu(){ID=4,Name="九阴真经",Power=80},
                new Kongfu(){ID=5,Name="孤独九剑",Power=60},
            };

            //用LINQ查询级别大于8的
            var res = from m in mastreList
                      where m.Level > 8
                      select m.Name;//表示把m的集合返回,可以选择要输出的内容   select m就全部输出
            foreach (var temp in res)
            {
                Console.WriteLine(temp);
            }
            Console.ReadKey();
        }
    }

注意要加以下的步骤，才能正常输出。

public override string ToString()
{
return string.Format(“ID:{0}, Name = :{1}, age =: {2}, MenPai = :{3}, KongFu = :{4}, Level =
:{5}”,ID,Name,age,MenPai,KongFu,Level);
}

LINQ联合查询：

var res = from m in mastreList
where m.Level > 8&&m.Menpai==“丐帮”
select m.Name;

扩展方法写法

    var res = mastreList.Where(m=>m.Level>8&&m.Menpai=="丐帮");

、

LINQ联合管理

                      var res = from m in mastreList
                      from k in kongfu
                      where m.KongFu==k.Name&&k.Power>85
                      select new { master = m, kongfu = k }; //选择要输出的内容

            foreach (var temp in res)
            {
                Console.WriteLine(temp);
            }
          

因为MartialArtsMaster没有武功的power，因此知道人名，想知道武功的power，就要从kongfu中去寻找。因此要用到LINQ联合管理。

上述程序的扩展方法用法：

 var res=mastreList.SelectMany(m=>kongfu,(m,k)=>new{master=m,kongfu=k})
                .Where(x=>x.master.KongFu==x.kongfu.Name&&x.kongfu.Power>85);
foreach (var temp in res)
            {
                Console.WriteLine(temp);
            }

对结果进行排序 orderby

 var res = from m in mastreList
                      where m.Level > 8
                      // orderby m.age  年龄从小到大排序
                      //orderby m.age,my.Level//先比较年龄，一样的话，再比较多等级排序
                      orderby m.age descending//按年龄从大到小排序

                     select m;//表示把m的集合返回,可以选择要输出的内容  

            foreach (var temp in res)
            {
                Console.WriteLine(temp);
            }

上述代码可以这样写

var res = mastreList.Where(m => m.Level > 8).OrderBy(m => m.age);

多个字段时

var res = mastreList.Where(m => m.Level > 8).OrderBy(m => m.age).ThenBy(m => m.Level);

var res = mastreList.Where(m => m.Level > 8).OrderBy(m => m.age).OrderBy(m => m.Level);
这样是错误的，是先按等级排，又按年龄重新排了一次

Join On联合集合查询

 var res = from m in mastreList
                      join k in kongfu on m.KongFu equals k.Name//用join on 做两个集合的连接
                      where k.Power>85
                      select new { master = m, kongFu = k };

            foreach (var temp in res)
            {
                Console.WriteLine(temp);
            }

对结果进行分组操作 into groups

var res = from k in kongfu
                      join m in mastreList on k.Name equals m.KongFu
                      into groups//按武功进行分组，看学什么武功的比较多
                      orderby groups.Count()
                      select new { kongfu = k, count = groups.Count() };
            foreach (var temp in res)
            {
                Console.WriteLine(temp);
            }

对结果进行分组操作 group by

var res = from m in mastreList
                      group m by m.MenPai into g//按门派进行分组
                      select new { count = g.Count(), key = g.Key };//g.Key表示按照哪个属性分的组

            foreach (var temp in res)
            {
                Console.WriteLine(temp);
            }

量词操作符any all
用来做判断是否存在或是否全是

> 存在： bool res = mastreList.Any(m => m.MenPai == "华山");  
> 全是： bool res = mastreList.All(m => m.MenPai == "华山");