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  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4.  
  5. public class Test
  6. {
  7. 	public static void Main()
  8. 	{
  9.             List<Destination> destinations = new List<Destination>() {
  10.                 new Destination() { A = 1, B = 1 },
  11.                 new Destination() { A = 1, B = 2 },
  12.                 new Destination() { A = 2, B = 1 }
  13.             };
  14.  
  15.             List<Source> sources = new List<Source>() {
  16.                 new Source() { A = 1, B = 1, C = "a" },
  17.                 new Source() { A = 2, B = 1, C = "b" },
  18.                 new Source() { A = 2, B = 1, C = "c" },
  19.                 new Source() { A = 1, B = 1, C = "d" },
  20.                 new Source() { A = 2, B = 2, C = "e" }
  21.             };
  22.  
  23.             var lookup = sources.ToLookup(s => new { s.A, s.B }, s => s.C);
  24.             foreach (var d in destinations)            
  25.                 d.Cs = lookup[new { d.A, d.B }].ToList();
  26.  
  27.             // results
  28.             Console.WriteLine("A B  Cs");
  29.             foreach(var d in destinations)
  30.             {
  31.                 Console.WriteLine("{0}-{1}: {2}", d.A, d.B, String.Join(",", d.Cs.Cast<string>().ToArray()));
  32.             }
  33. 	}
  34. }
  35.  
  36. class Source
  37. {
  38.     public object A { get; set; }
  39.     public object B { get; set; }
  40.     public object C { get; set; }
  41. }
  42.  
  43. class Destination
  44. {
  45.     public object A { get; set; }
  46.     public object B { get; set; } // (A,B) is a unique key
  47.     public List<object> Cs { get; set; }
  48.     public object D { get; set; }
  49. }
Success #stdin #stdout 0.05s 33992KB
comments (?)
stdin 
Standard input is empty
stdout 
A B  Cs
1-1: a,d
1-2: 
2-1: b,c
https://ideone.com/8Xl3eA
language:
C# (gmcs 5.20.1)
created:
12 years ago
visibility:
secret

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