Linq基本子句介绍-语法之select

 Linq表达式的查询结果，是通过select得到的。select可以 进行数据转化工作，得到你想要的数据结果。

一、创建控制台应用程序DemoSelect_1

二、添加类 PersonInfo.cs

 

/// <summary>
    /// 人物类
    /// </summary>
    public class PersonInfo
    {
        /// <summary>
        /// 姓名
        /// </summary>
        public string Name { get; set; }

        /// <summary>
        /// 国家
        /// </summary>
        public string Country { get; set; }

        /// <summary>
        /// 职位
        /// </summary>
        public string Official { get; set; }

        /// <summary>
        /// 薪水
        /// </summary>
        public int Salary { get; set; }

        /// <summary>
        /// 是否为魏国
        /// </summary>
        /// <param name="country"></param>
        /// <returns></returns>
        public bool IsWei(string country)
        {
            if (country == "魏")
                return true;
            else
                return false;
        }

        /// <summary>
        /// 替换主公名字
        /// </summary>
        public string ReplaceName(string name)
        {
            if(name=="刘备")
                return "刘禅";
            if (name == "曹操")
                return "曹丕";
            if (name == "孙权")
                return "孙亮";
            return name;
        }
    }

三、添加类 ShortInfo.cs

/// <summary>
    /// 简短信息
    /// </summary>
    public class ShortInfo
    {
        public ShortInfo(string name, string country)
        {
            this.Name = name;
            this.Country = country;
        }

        /// <summary>
        /// 姓名
        /// </summary>
        public string Name { get; set; }

        /// <summary>
        /// 国家
        /// </summary>
        public string Country { get; set; }
    }

四、加入代码到Program.cs

 

class Program
    {
        static void Main(string[] args)
        {
            // 填充数据
            List<PersonInfo> pList = new List<PersonInfo>()
            {
                new PersonInfo(){ Name="刘备", Country="蜀", Official="皇帝", Salary=10000},
                new PersonInfo{ Name="关羽", Country="蜀", Official="上将", Salary=10000},
                new PersonInfo{ Name="张飞", Country="蜀", Official="上将", Salary=10000},

                new PersonInfo{ Name="曹操", Country="魏", Official="皇帝", Salary=10000},
                new PersonInfo{ Name="典韦", Country="魏", Official="上将", Salary=8000},
                new PersonInfo{ Name="许褚", Country="魏", Official="上将", Salary=8000},

                new PersonInfo{ Name="孙权", Country="吴", Official="皇帝", Salary=10000},
                new PersonInfo{ Name="周瑜", Country="吴", Official="都督", Salary=8000},
                new PersonInfo{ Name="陆逊", Country="吴", Official="都督", Salary=8000}

            };

            // 简单select
            Console.WriteLine("******************简单select******************");
            var query = from v in pList
                        where v.Name == "刘备"
                        select v;

            foreach (PersonInfo p in query)
            {
                Console.WriteLine(string.Format("姓名:{0}---国家:{1}---职位:{2}---薪水:{3}" , p.Name,p.Country,p.Official,p.Salary));
            }

            Console.ReadKey();

            // 输出某个属性的select
            Console.WriteLine("******************输出某个属性的select******************");
            var query_1 = from v in pList
                          where v.Country == "蜀"
                          select v.Name;

            foreach (string p in query_1)
            {
                Console.WriteLine(string.Format("姓名:{0}",p));
            }
            Console.ReadKey();

            // 用自定义函数，替换属性值，然后输出的select
            Console.WriteLine("******************替换属性值，然后输出的select******************");
            var query_2 = from v in pList
                          where v.Official == "皇帝"
                          select new PersonInfo().ReplaceName(v.Name);

            foreach (string p in query_2)
            {
                Console.WriteLine(string.Format("姓名:{0}", p));
            }
            Console.ReadKey();

            // 转换为需要的类型
            Console.WriteLine("******************替换属性值，然后输出的select******************");
            var query_3 = from v in pList
                          select new ShortInfo(v.Name,v.Country);

            foreach (ShortInfo p in query_3)
            {
                Console.WriteLine(string.Format("姓名:{0}---国家：{1}", p.Name,p.Country));
            }
            Console.ReadKey();

        }
    }

 

运行结果：