C# List的使用

1、List排序

　　採用自定義Sort比較器和Linq

class Persion
    {
        public string name;
        public int age;
}
//自定義Sort方法
private static void sortListClass()
        {
            Persion p1 = new Persion() { name = "huyong", age = 27 };
            Persion p2 = new Persion() { name = "tansha", age = 25 };
            List<Persion> listPersion = new List<Persion>();
            listPersion.Add(p1);
            listPersion.Add(p2);
            listPersion.Sort(sortage);
            foreach (var item in listPersion)
            {
                Console.WriteLine(item.name + ":" + item.age);
            }
        }
        static int sortage(Persion x, Persion y)
        {
            if (x.age < y.age) return -1;                //按age從大到小 降序排列
            else if (x.age == y.age) return 0;
            else return 1;
        }
//linq方法
 private static void sortLinq()
        {
            Persion p1 = new Persion() { name = "huyong", age = 27 };
            Persion p2 = new Persion() { name = "tansha", age = 25 };
            Persion p3 = new Persion() { name = "tansha", age = 27 };
            List<Persion> listPersion = new List<Persion>();
            listPersion.Add(p1);
            listPersion.Add(p2);
            listPersion.Add(p3);

 var lList = from t in listPersion where (t.age == 27) orderby t.name ascending select t;
            foreach (var item in lList)
            {
                Console.WriteLine(item.name + ":" + item.age);
            }
        }

View Code

 

2、用Linq將兩個list合併爲一個list

  //linq合併兩個list,根據某一相同字段
private static void mergeList()
        {
            Persion p1 = new Persion() { name = "hy", province = "jx" };
            Persion p2 = new Persion() { name = "tansha", province = "hn" };
            Persion p3 = new Persion() { name = "ht", province = "gd" };
            List<Persion> listPersion = new List<Persion>();
            listPersion.Add(p1);
            listPersion.Add(p2);
            listPersion.Add(p3);

            Persion p11 = new Persion() { name = "hy", age = 23, sex = "男" };
            Persion p21 = new Persion() { name = "tansha", age = 12, sex = "女" };
            Persion p31 = new Persion() { name = "ht", age = 7, sex = "男" };
            List<Persion> listPersion2 = new List<Persion>();
            listPersion2.Add(p11);
            listPersion2.Add(p21);
            listPersion2.Add(p31);

            //linq合併兩個list,根據某一相同字段
            var list = from pp1 in listPersion
                       join pp2 in listPersion2 on pp1.name equals pp2.name
                       select new Persion
                       {
                           name = pp1.name,
                           province = pp1.province,
                           age = pp2.age,
                           sex = pp2.sex
                       };
            foreach (var item in list)
            {
                Console.WriteLine(item.name + ":" + item.age + ":" + item.sex + ":" + item.province);
            }
        }

View Code

 

3、對List裏面的某個數據進行操做並保存

lists.Where(q =>q.SellChannelId == ((int)SellChannelType.PB).ToString()).ToList().ForEach(q => q.index = 10);

4、List<T>轉化爲IQueryable<T>

　　不能直接轉換，

IQueryable在數據庫端中查詢，

IEnumerable在內存上查詢。

List<T>支持後者。能夠用 list.AsQueryable<T>轉換。