Linq的一些操作

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;

namespace LinqToObject
{
    public class LinqToDataTable
    {
        public static void LinqToDt()
        {
            DataTable dt = new DataTable();
            
            dt.Columns.Add("Name", typeof(string));
            dt.Columns.Add("Sex", typeof(string));
            dt.Columns.Add("Age", typeof(int));

            for (int i = 0; i < 100; i++)
            {
                DataRow dr = dt.NewRow();
                if (i > 50)
                {
                    dr["Name"] = "cbs";
                    dr["Sex"] = "male";
                }
                else
                {
                    dr["Name"] = "cbs2";
                    dr["Sex"] = "female";
                }
                dr["Age"] = i;
                dt.Rows.Add(dr);
            }
            DataTable dtResult = dt.Clone();
            //使用where
            var var_dt = dt.AsEnumerable().Where<DataRow>(ss=>ss["Name"].ToString()=="cbs");
            int count = var_dt.Count<DataRow>(); //获取dt中Name 名为cbs的数量

            //使用Average
            var avg_dt = dt.AsEnumerable().Average<DataRow>(pp => float.Parse(pp["Age"].ToString()));

            //使用GroupBy
            var groupby_dt = dt.AsEnumerable().GroupBy(G => G["Name"].ToString()) //根据Name分组
                .Select(S => new { //分组统计
                Name = S.Key, //分组的值
                SumName=S.Sum(sm=>sm.Field<int>("Age")),
                CountName = S.Count(sc=>sc.Field<int>("Age")==2)
            });
            groupby_dt.ToList().ForEach(f=>dtResult.Rows.Add(f.Name,f.SumName,f.CountName));

            //使用Orderby
            var orderby_dt = dt.AsEnumerable().OrderBy(o=>o["Age"]).CopyToDataTable();
            dt = dt.AsEnumerable().OrderByDescending(o => o["Age"]).CopyToDataTable();

            //使用Distinct
            dt = dt.AsEnumerable().Distinct().CopyToDataTable();

            //查询
            var rows = dt.Select("Name='cbs'");

            var q1 = from d in dt.AsEnumerable()
                     where d.Field<string>("Name") == "cbs"
                     group d by d.Field<string>("Sex")
                     into m
                     select new
                     {
                         Name = m.Key,
                        // CountName=m.Count(n=>n.Field<DateTime?>("Name").HasValue)  可为空的有HasValue属性判断是否有值
                     };

            var mm = from d in dt.AsEnumerable()
                    where d.Field<string>("Name") == "cbs"
                    select new Item
                    {
                        Name=d.Field<string>("Name"),
                        Sex=d.Field<string>("Sex")
                    };

        }

        public class Item
        {
            public string Name { get; set; }
            public string Sex { get; set; }
        }
    }
}