linq 分类汇总加计算。

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

namespace 学生成绩Linq
{
    class Student
    {
        public string LastName;
        public List<int> Scores;
        public Student()
        { 
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            List<Student> students = new List<Student> { new Student
            {
                LastName="xiaogui",Scores=new List<int>{97,42,91,60}}, new Student
                {
                    LastName="xiaozhan",Scores=new List<int>{50,92,81,60}}, new Student
                    {
                        LastName="xiaolan",Scores=new List<int>{32,32,81,90}}, new Student
                        {
                            LastName="xiaowan",Scores=new List<int>{92,22,81,60}},
        }; var query = from stuent in students
                       from score in stuent.Scores
                       where score > 90
                       select new
                       {
                           Last = stuent.LastName,
                           score
                       };
            foreach (var student in query)//大于90分的显示出来   
            {
                Console.WriteLine("{0} Score:{1}", student.Last, student.score);
            }
            

            DataTable dt = new DataTable();
            dt.Columns.Add("编号", typeof(string));
            dt.Columns.Add("单价", typeof(Int32));
            dt.Columns.Add("数量", typeof(Int32));
            dt.Rows.Add("标识1", 100,11);
            dt.Rows.Add("标识2", 30,5);
            dt.Rows.Add("标识2", 40,5);
            dt.Rows.Add("标识3", 80,20);
            var query1 = from c in dt.AsEnumerable()
                        group c by c.Field<string>("编号")
                into g
                         let c = g.First().Field<Int32>("数量")
                         select new
                        {
                            zhujian = g.Key,
                            tongji = g.Sum(s => s.Field<Int32>("单价")),
                            danjia=c,
                            zj= g.Sum(s => s.Field<Int32>("单价")) * c
                        };
            Console.WriteLine("编号" + "                    数量                    单价                    合计" + "\n" + "=================");
            foreach (var item in query1)
            {
                Console.WriteLine("" + item.zhujian + "                    " + item.tongji + "                    " + item.danjia + "                    " + item.zj);
            }

            Console.ReadLine();
        }        

}
}

xiaogui Score:97
xiaogui Score:91
xiaozhan Score:92
xiaowan Score:92
编号                    数量                    单价                    合计
=================
标识1                    100                    11                    1100
标识2                    70                    5                    350
标识3                    80                    20                    1600

linq 分类汇总 加 计算。

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linq 分类汇总加计算。