CODEWITHSUNDEEP
c#linq
MrX
MrX

Reputation: 424

c# reversing and serializing a dictionary using linq

Was wondering is it possible to reverse a dictionary in a single LINQ statement?

The structure is as follows;

Dictionary<string, List<string>> original = new Dictionary<string, List<string>>() 
    {
        {"s", new List<string>() { "1", "2", "3" }},
        {"m", new List<string>() { "4", "5", "6" }},
        {"l", new List<string>() { "7", "8", "9" }},
        {"xl", new List<string>() { "10", "11", "12" }},
    };

which i would like to convert to a dictionary of type;

Dictionary<string, string> Reverse = new Dictionary<string, string>()
    {
        {"1", "s"},
        {"2", "s"}, //and so on
    };

Upvotes: 2

Views: 374

Answers (4)

sloth
sloth

Reputation: 101052

Something like:

var result = (from kvp in original
              from value in kvp.Value
              select new {Key = value, Value = kvp.Key}).ToDictionary(a => a.Key, a => a.Value);

Or, if you prefer the method syntax:

var result = original.SelectMany(kvp => kvp.Value.Select(v => new {Key = v, Value = kvp.Key}))
                     .ToDictionary(a => a.Key, a => a.Value);

Upvotes: 2

Eoin Campbell
Eoin Campbell

Reputation: 44268

you can use a SelectMany to split the value sublists, and then reverse the Keys & Values into a new Dictionary using ToDictionary

var result = original
    .SelectMany(k=> k.Value.Select(v => new { Key = v, Value = k.Key } ))
    .ToDictionary( t=> t.Key, t=> t.Value);

Upvotes: 1

Erik Schierboom
Erik Schierboom

Reputation: 16636

For that you can use the SelectMany LINQ extension method:

var original = new Dictionary<string, List<string>>
                   {
                       { "s", new List<string> { "1", "2", "3" } },
                       { "m", new List<string> { "4", "5", "6" } },
                       { "l", new List<string> { "7", "8", "9" } },
                       { "xl", new List<string> { "10", "11", "12" } },
                   };

var keyValuePairs = original.SelectMany(o => o.Value.Select(v => new KeyValuePair<string, string>(v, o.Key)));

Upvotes: 1

Patryk Ćwiek
Patryk Ćwiek

Reputation: 14318

If you do:

var reversed = original.SelectMany(x => x.Value.Select(y => new KeyValuePair<string, string>(y, x.Key)));

then you get:

1 - s

2 - s

3 - s

4 - m

5 - m

etc.

Upvotes: 2

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