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  1. using System;
  2. using System.Linq;
  3. using System.Collections.Generic;
  4.  
  5. public class Test
  6. {
  7. 	public static void Main()
  8. 	{
  9.         List<TestItem> list = new List<TestItem>();
  10.         list.Add( new TestItem { Id = 1, Field1 = 1});
  11.         list.Add( new TestItem { Id = 1, Field1 = 2});
  12.         list.Add( new TestItem { Id = 2, Field1 = 3});
  13.         list.Add( new TestItem { Id = 2, Field1 = 4});
  14.  
  15.         var indexList = list
  16.             .GroupBy(item => item.Id)
  17.             .SelectMany(grp => grp
  18.                 .Select((t, index) => new { index = index, t }));
  19.  
  20.  
  21.         foreach (var t in indexList)
  22.         {
  23.             Console.WriteLine("ID: " + t.t.Id + " ---- Index:" + t.index);
  24.         }		
  25. 	}
  26. }
  27.  
  28. public class TestItem
  29. {
  30.    public int Id { get; set;}
  31.    public int Field1 { get; set; }
  32.    public int Field2 { get; set; }
  33. }
  34.  
Success #stdin #stdout 0.05s 34152KB
comments ()
stdin
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Standard input is empty
stdout
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ID: 1 ---- Index:0
ID: 1 ---- Index:1
ID: 2 ---- Index:0
ID: 2 ---- Index:1
https://ideone.com/nSTa8A
language:
C# (gmcs 5.20.1)
created:
11 years ago
visibility:
public

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