how to union 2 dictionaries

Question

Possible Duplicate:
Merging dictionaries in C#

using c#4 having 2 dictionaries of type

<string,List<int>>



dictionary1 = [ { "key1" , [ 1, 2, 3]} ,
                 { "key2" , [ 1, 2, 4 , 6]}
              ]

I want to union with dictionary2

dictionary2 = [ { "key0" , [ 1, 2, 3]} ,
                 { "key2" , [ 1, 2, 3, 5 , 6]} 
              ]

so to get =>

dictionary1 + dictionary2  = [ { "key1" , [ 1, 2, 3]} ,
                 { "key2" , [ 1, 2, 3, 4, 5, 6]},
                 { "key0" , [ 1, 2, 3]}
              ]

how can I do it ?

@Candide It does not look like an answer the OP is looking for, because he is looking for a two-way merge. — Sergey Kalinichenko, Nov 24 '12 at 20:23
By the way, do you allow duplicates inside the list of integers? (I mean `{ "key1" , { 1, 2, 2, 3, 3, 3 }}`.) — Sergey Vyacheslavovich Brunov, Nov 24 '12 at 20:31
If you want a LINQ approach: http://stackoverflow.com/a/4792130/1149773 — Douglas, Nov 24 '12 at 20:31
I'm voting to reopen because the so-called "duplicate" question seems to be referring to lists of dictionaries rather than 2 dictionaries — Sam I am says Reinstate Monica, Apr 01 '14 at 22:45
I agree @SamIam, this question needs to merge values as well as the whole dictionary. — JasonMArcher, Apr 01 '14 at 23:05

Tim Schmelter · Answer 1 · 2012-11-24T22:08:19.087

5

A simple loop with Enumerable.Union?:

foreach (var kv in dictionary2)
{
    List<int> values;
    if (dictionary1.TryGetValue(kv.Key, out values))
    {
        dictionary1[kv.Key] = values.Union(kv.Value).ToList();
    }
    else
    {
        dictionary1.Add(kv.Key, kv.Value);
    }
}

edited Nov 24 '12 at 22:08

answered Nov 24 '12 at 20:21

Tim Schmelter

450,073
74
686
939

1

@Haddar: fyi, edited my answer since my first version was buggy. – Tim Schmelter Nov 24 '12 at 22:12
I took @L.B example, 10X – Haddar Macdasi Nov 24 '12 at 22:13

score 2 · Accepted Answer · answered Nov 24 '12 at 20:33

2

var result = 
   dictionary1.Union(dictionary2)
    .GroupBy(kv => kv.Key)
    .ToDictionary(g => g.Key, g => g.SelectMany(v => v.Value).Distinct().ToList());

answered Nov 24 '12 at 20:33

L.B

114,136
19
178
224

how to union 2 dictionaries

2 Answers2