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  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4.  
  5. static class Program
  6. {
  7.     static void Main(string[] args)
  8.     {
  9.         var ax = new[] { 
  10.             new { id = 1, name = "John" },
  11.             new { id = 2, name = "Sue" } };
  12.         var bx = new[] { 
  13.             new { id = 1, surname = "Doe" },
  14.             new { id = 3, surname = "Smith" } };
  15.  
  16.         ax.FullOuterJoin(
  17.                 bx, a => a.id, b => b.id,
  18.                 (a, b, id) => new { a.name, b.surname },
  19.                 new { id = -1, name = "(no firstname)" },
  20.                 new { id = -2, surname = "(no surname)" }
  21.             )
  22.             .ToList().ForEach(Console.WriteLine);
  23.     }
  24. }
  25.  
  26. internal static class MyExtensions
  27. {
  28.     internal static IList<TR> FullOuterGroupJoin<TA, TB, TK, TR>(
  29.         this IEnumerable<TA> a,
  30.         IEnumerable<TB> b,
  31.         Func<TA, TK> selectKeyA, 
  32.         Func<TB, TK> selectKeyB,
  33.         Func<IEnumerable<TA>, IEnumerable<TB>, TK, TR> projection,
  34.         IEqualityComparer<TK> cmp = null)
  35.     {
  36.         cmp = cmp?? EqualityComparer<TK>.Default;
  37.         var alookup = a.ToLookup(selectKeyA, cmp);
  38.         var blookup = b.ToLookup(selectKeyB, cmp);
  39.  
  40.         var keys = new HashSet<TK>(alookup.Select(p => p.Key), cmp);
  41.         keys.UnionWith(blookup.Select(p => p.Key));
  42.  
  43.         var join = from key in keys
  44.                    let xa = alookup[key]
  45.                    let xb = blookup[key]
  46.                    select projection(xa, xb, key);
  47.  
  48.         return join.ToList();
  49.     }
  50.  
  51.     internal static IList<TR> FullOuterJoin<TA, TB, TK, TR>(
  52.         this IEnumerable<TA> a,
  53.         IEnumerable<TB> b,
  54.         Func<TA, TK> selectKeyA, 
  55.         Func<TB, TK> selectKeyB,
  56.         Func<TA, TB, TK, TR> projection,
  57.         TA defaultA = default(TA), 
  58.         TB defaultB = default(TB),
  59.         IEqualityComparer<TK> cmp = null)
  60.     {
  61.         cmp = cmp?? EqualityComparer<TK>.Default;
  62.         var alookup = a.ToLookup(selectKeyA, cmp);
  63.         var blookup = b.ToLookup(selectKeyB, cmp);
  64.  
  65.         var keys = new HashSet<TK>(alookup.Select(p => p.Key), cmp);
  66.         keys.UnionWith(blookup.Select(p => p.Key));
  67.  
  68.         var join = from key in keys
  69.                    from xa in alookup[key].DefaultIfEmpty(defaultA)
  70.                    from xb in blookup[key].DefaultIfEmpty(defaultB)
  71.                    select projection(xa, xb, key);
  72.  
  73.         return join.ToList();
  74.     }
  75. }
  76.  
Success #stdin #stdout 0.07s 34352KB
comments (?)
stdin 
Standard input is empty
stdout 
{ name = John, surname = Doe }
{ name = Sue, surname = (no surname) }
{ name = (no firstname), surname = Smith }
https://ideone.com/kG4kqO
language:
C# (gmcs 5.20.1)
created:
11 years ago
visibility:
secret

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