在 Linq 中使用交叉连接/透视

Question

我有一个具有以下结构的集合。

List<QuestionAnswer> answers = new List<QuestionAnswer>(){};

class QuestionAnswer
{
  string Question { get; set; }
  string Answer { get; set; }
}

它填充了以下数据：

Question Answer
Q1       a
Q1       b
Q2       c
Q2       d
Q2       e

我需要将其转换为以下格式：

Q1   Q2
 a   c
 a   d
 a   e
 b   c
 b   d
 b   e

问题直到运行时才知道；集合中可能有 n 个问题。我相信我需要自行交叉加入集合，并以某种方式将问题显示为标题（枢轴行和列）。我无法生成目标数据格式。任何帮助表示赞赏。

Answer 1

你可以这样做

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            List<QuestionAnswer> answers = new List<QuestionAnswer>() { 
                new QuestionAnswer() { Question = "Q1", Answer = "a"},
                new QuestionAnswer() { Question = "Q1", Answer = "b"},
                new QuestionAnswer() { Question = "Q2", Answer = "c"},
                new QuestionAnswer() { Question = "Q2", Answer = "d"},
                new QuestionAnswer() { Question = "Q2", Answer = "e"},
            };

            DataTable dt = new DataTable();
            List<string> uniqueQuestions = answers.Select(x => x.Question).Distinct().ToList();

            foreach (string question in uniqueQuestions)
            {
                dt.Columns.Add(question, typeof(string));
            }

            var groups = answers.GroupBy(x => x.Answer).ToList();

            foreach (var group in groups)
            {
                DataRow newRow = dt.Rows.Add();
                foreach (QuestionAnswer qA in group)
                {
                    newRow[qA.Question] = qA.Answer;
                }
            }

        }
    }
    public class QuestionAnswer
    {
        public string Question { get; set; }
        public string Answer { get; set; }
    }
}

提供以下内容：