Question

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

class MergeTwoCSVFiles
    {
        static void Main()
        {
            // See section Compiling the Code for information about the data files.
            string[] names = System.IO.File.ReadAllLines(@"c:\users\mypc\documents\visual studio 2017\Projects" + 
            @"\CustomJoinsLinq_cs\CustomJoinsLinq_cs\names.csv");
            string[] scores = System.IO.File.ReadAllLines(@"c:\users\mypc\documents\visual studio 2017\Projects" + 
            @"\CustomJoinsLinq_cs\CustomJoinsLinq_cs\scores.csv");

            // Merge the data sources using a named type.
            // You could use var instead of an explicit type for the query.
             IEnumerable<Student> queryNamesScores =
                 // Split each line in the data files into an array of strings.
                 from name in names
                 let x = name.Split(',')
                 from score in scores
                 let s = score.Split(',')
                 // Look for matching IDs from the two data files.
                 where x[2] == s[0]
                 // If the IDs match, build a Student object.
                 select new Student()
                 {
                     FirstName = x[0],
                     LastName = x[1],
                     ID = Convert.ToInt32(x[2]),
                     ExamScores = (from scoreAsText in s.Skip(1)
                               select Convert.ToInt32(scoreAsText)).
                               ToList()
                 };

             // Optional. Store the newly created student objects in memory
             // for faster access in future queries
             List<Student> students = queryNamesScores.ToList();

             foreach (var student in students)
             {
                 Console.WriteLine("The average score of {0} {1} is {2}.",
                 student.FirstName, student.LastName, student.ExamScores.Average());
             }

            /*foreach (var item in scores)
            {
                Console.WriteLine(item);
            }*/

            //Keep console window open in debug mode
            Console.WriteLine("Press any key to exit.");
            Console.ReadKey();
        }
    }

    class Student
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int ID { get; set; }
        public List<int> ExamScores { get; set; }
    }

嗨，大家好请在运行上述程序时，只需按任意键即可退出。显示，这是程序的退出。它应该显示查询执行的结果，但事实并非如此。在调试模式下，注意到获取的数据源（在上面的一个数据源上执行了每个数据源，并且工作正常），但是查询没有被创建，因此无法获得执行。得分数组的字符串数据源在scores.csv文件中包含12行，但在调试模式下将得分数组的字符串添加到监视窗口，表示该数组长度为14.不知道这些是否有任何关系用它。这两个类都在同一个命名空间，我没有在这里显示请有人帮忙。我正在使用2017年的视觉工作室干杯

Linq查询未创建

0 个答案: