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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(bx, a => a.id, b => b.id, (a, b, id) => new {a, b})
  17. 			.ToList().ForEach(Console.WriteLine);
  18. 	}
  19. }
  20.  
  21. internal static class MyExtensions
  22. {
  23.     internal static IList<TR> FullOuterGroupJoin<TA, TB, TK, TR>(
  24.         this IEnumerable<TA> a,
  25.         IEnumerable<TB> b,
  26.         Func<TA, TK> selectKeyA, 
  27.         Func<TB, TK> selectKeyB,
  28.         Func<IEnumerable<TA>, IEnumerable<TB>, TK, TR> projection,
  29.         IEqualityComparer<TK> cmp = null)
  30.     {
  31.         cmp = cmp?? EqualityComparer<TK>.Default;
  32.         var alookup = a.ToLookup(selectKeyA, cmp);
  33.         var blookup = b.ToLookup(selectKeyB, cmp);
  34.  
  35.         var keys = new HashSet<TK>(alookup.Select(p => p.Key), cmp);
  36.         keys.UnionWith(blookup.Select(p => p.Key));
  37.  
  38.         var join = from key in keys
  39.                    let xa = alookup[key]
  40.                    let xb = blookup[key]
  41.                    select projection(xa, xb, key);
  42.  
  43.         return join.ToList();
  44.     }
  45.  
  46.     internal static IList<TR> FullOuterJoin<TA, TB, TK, TR>(
  47.         this IEnumerable<TA> a,
  48.         IEnumerable<TB> b,
  49.         Func<TA, TK> selectKeyA, 
  50.         Func<TB, TK> selectKeyB,
  51.         Func<TA, TB, TK, TR> projection,
  52.         TA defaultA = default(TA), 
  53.         TB defaultB = default(TB),
  54.         IEqualityComparer<TK> cmp = null)
  55.     {
  56.         cmp = cmp?? EqualityComparer<TK>.Default;
  57.         var alookup = a.ToLookup(selectKeyA, cmp);
  58.         var blookup = b.ToLookup(selectKeyB, cmp);
  59.  
  60.         var keys = new HashSet<TK>(alookup.Select(p => p.Key), cmp);
  61.         keys.UnionWith(blookup.Select(p => p.Key));
  62.  
  63.         var join = from key in keys
  64.                    from xa in alookup[key].DefaultIfEmpty(defaultA)
  65.                    from xb in blookup[key].DefaultIfEmpty(defaultB)
  66.                    select projection(xa, xb, key);
  67.  
  68.         return join.ToList();
  69.     }
  70. }
  71.  
Success #stdin #stdout 0.07s 34376KB
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stdin
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Standard input is empty
stdout
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{ a = { id = 1, name = John }, b = { id = 1, surname = Doe } }
{ a = { id = 2, name = Sue }, b =  }
{ a = , b = { id = 3, surname = Smith } }
https://ideone.com/O36nWc
language:
C# (gmcs 5.20.1)
created:
10 years ago
visibility:
secret

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