在列表中查找对象的并集(复合对象/嵌套列表)

据我所知，您需要这样的东西。（我使用的是VS2010和C#4，但任何支持LINQ的版本都应该这样做）。

using System;
using System.Collections.Generic;
using System.Linq;
namespace SO6299404
{
    class Author
    {
        public string FirstName;
        public string LastName;
    }
    class Magazine
    {
        public string Title;
        public string ISBN;
        public List<Article> TOC;

        // Code Until the end of the class is for testing only
        public void Dump()
        {
            Dump(0);
        }
        public void Dump(int indent)
        {
            Console.WriteLine("".PadLeft(indent) + Title);
            if (TOC != null)
            {
                foreach (Article article in TOC)
                {
                    article.Dump(indent + 2);
                }
            }
        }
    }
    class Article
    {
        public string Title;
        public string Header;
        public string Body;
        public int PageNumber;
        public Magazine Source;
        public Author Author;
        // Code Until the end of the class is for testing only
        public void Dump()
        {
            Dump(0);
        }
        public void Dump(int indent)
        {
            string author = Author == null ? "" : Author.FirstName;
            Console.WriteLine("".PadLeft(indent) + Title + ", " + author);
        }
    }
    // A foreach extension. Not strictly nescessary, but having this extension
    // makes it a bit easier to write foreach loops
    public static class EnumerableExtension
    {
        public static void Foreach<T>(this IEnumerable<T> enumerable, Action<T> action)
        {
            if (enumerable == null) throw new ArgumentNullException("enumerable");
            if (action == null) throw new ArgumentNullException("action");
            foreach (T value in enumerable)
                action(value);
        }
    }
    class Program
    {
        static void Main()
        {
            List<Magazine> magazines = SetupTestCase();
            // Let's print out our test case
            Console.WriteLine("==[Setup]===========================");
            magazines.Foreach(x => x.Dump());
            // So now we need to extraxct all Authors and list articles belonging to them
            // First we get Authorl; Article pair and then we group by Authors
            var temp = magazines.SelectMany(m => m.TOC, (a, b) => new {b.Author, Article = b}).GroupBy(x => x.Author);
            // Ok, we are done. Let's print out the results
            Console.WriteLine("==[REsult]===========================");
            temp.Foreach(x =>
            {
                Console.WriteLine(x.Key.FirstName);
                x.Foreach( y => y.Article.Dump(2));
            });
        }
        // The code from here until the end of the class is for generating a test case only
        private static List<Magazine> SetupTestCase()
        {
            // Let's set up a test case similar to the example in the question
            // We generate 5 Authors
            Author[] authors = Seed(1, 5).Select(x => GenerateTestAuthor(x.ToString())).ToArray();
            // And 9 Articles
            Article[] articles = Seed(1,9).Select(x => GenerateTestArticle(x.ToString())).ToArray();
            // This defines how articles are connected to authors
            int[] articleToAuthor = new[] {0,1,2,3,4,3,2,1,0};
            // Let's connect articles and authors as per definition abbove
            Seed(9).Foreach(x=> {articles[x].Author = authors[articleToAuthor[x]];});
            // Now 3 Magazines
            Magazine[] magazines = Seed(1,3).Select(x => GenerateTestMagazine(x.ToString())).ToArray();
            // This deines which articles go in which magazine
            int[] articleToMagazine = new[] {0,0,0,1,1,1,2,2,2};
            // Let's add artices to the Magazines
            Seed(9).Foreach(x=> magazines[articleToMagazine[x]].TOC.Add(articles[x]));
            // And now let us link back from articles to Magazines
            magazines.Foreach(x => x.TOC.Foreach(z => z.Source = x));
            return magazines.ToList();
        }
        static IEnumerable<int> Seed(int start, int count)
        {
            return Enumerable.Range(start, count);
        }
        static IEnumerable<int> Seed(int n)
        {
            return Seed(0, n);
        }
        static Article GenerateTestArticle(string id)
        {
            return new Article
            {
                Title = "Title" + id,
                Header = "Title" + id,
                Body = "Title" + id,
                PageNumber = 1,
            };
        }
        static Author GenerateTestAuthor(string id)
        {
            return new Author
            {
                FirstName = "Author" + id,
                LastName = "Author" + id,
            };
        }
        static Magazine GenerateTestMagazine(string id)
        {
            return new Magazine
            {
                Title = "Magazine" + id,
                ISBN = "Magazine" + id,
                TOC = new List<Article>()
            };
        }
    }
}

当我运行时，这就是我在屏幕上看到的

==[Setup]===========================
Magazine1
    Title1, Author1
    Title2, Author2
    Title3, Author3
Magazine2
    Title4, Author4
    Title5, Author5
    Title6, Author4
Magazine3
    Title7, Author3
    Title8, Author2
    Title9, Author1
==[REsult]===========================
Author1
    Title1, Author1
    Title9, Author1
Author2
    Title2, Author2
    Title8, Author2
Author3
    Title3, Author3
    Title7, Author3
Author4
    Title4, Author4
    Title6, Author4
Author5
    Title5, Author5

这是否适合您的需求？

  public class Student
  {
    public List<Course> Courses { get; set; }
    public List<Grade> Grades { get; set; }
    public Dictionary<Course, Grade> CourseGrades { get; set; }
  }
  public class Course
  {
    public int Id { get; set; }
  }
  public class Grade
  {
    public double Value { get; set; }
  }
  class Program
  {
    static void Main(string[] args)
    {
      var c0 = new Course() { Id = 0 };
      var c1 = new Course() { Id = 1 };
      var students = new List<Student>()
      {
        new Student() { CourseGrades = new Dictionary<Course,Grade>()
        { 
          { c0, new Grade() { Value = 2 } },
          { c1 , new Grade() { Value = 1 } }
        }},
        new Student() { CourseGrades = new Dictionary<Course,Grade>()
        { 
          { c1 , new Grade() { Value = 3 } },
          { c0 , new Grade() { Value = 4 } }
        }},
      };

      Dictionary<Course, List<Grade>> courseGrades = SelectUnion(students.SelectMany(s => s.CourseGrades), cg => cg.Key, cg => cg.Value);
    }
    private static Dictionary<TKey, List<TValue>> SelectUnion<TSource, TKey, TValue>(IEnumerable<TSource> set, Func<TSource, TKey> keyGen, Func<TSource, TValue> valueGen)
    {
      var result = new Dictionary<TKey, List<TValue>>();
      foreach (var src in set)
      {
        var key = keyGen(src);
        if (!result.ContainsKey(key))
        {
          result[key] = new List<TValue>();
        }
        result[key].Add(valueGen(src));
      }
      return result;
    }

我知道这很可能只适合你举的例子。因此，如果这还不够，也许你可以提供一个你想要的最终结果的示例结构，这样我们就知道该为什么拍摄了。