Dictionary with multiple values for each key?

Question

I want the functionality of a Dictionary, but I want to store multiple values for each key. How can this be done in .NET/C#? Is there any built in collection that supports this scenario?

If I do the following:

collection.Add("key1", new Order(1));
collection.Add("key1", new Order(2));
collection.Add("key1", new Order(3));
collection.Add("key2", new Order(4));

Then running the following should return 3 orders.

collection["key1"];

http://stackoverflow.com/questions/2101069/c-sharp-dictionary-one-key-many-values — Sajeetharan, Apr 08 '14 at 12:33
If you have already a collection of orders and a key you could use `ToLookup` which returns exactly what you want. http://stackoverflow.com/a/1403499/284240 — Tim Schmelter, Apr 08 '14 at 12:34

score 7 · Accepted Answer · answered Apr 08 '14 at 12:30

7

Simple: Use Dictionary<string,List<Order>>

answered Apr 08 '14 at 12:30

Sriram Sakthivel

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score 1 · Answer 2 · answered Apr 08 '14 at 12:31

1

You may use lists for this purpose, if the number of orders per key needs to be variable.

collection.Add("key1"), new List<order>(){new Order(1), new Order(2)});

answered Apr 08 '14 at 12:31

selkathguy

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score 1 · Answer 3 · answered Apr 08 '14 at 12:31

1

I would recommend using a List, Set, or Dictionary as appropriate for your Value in your Dictionary.

For example, you might do:

Dictionary<string, List<string>>

answered Apr 08 '14 at 12:31

ErikusMaximus

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score 1 · Answer 4 · answered Apr 08 '14 at 12:32

You should think about this in a different way. The Dictionary can hold a list of Orders rather than just a single one, like so:

var collection = Dictionary<string,List<Order>>();

collection.Add("key1", new List<Order>(new { new Order(1), new Order(2),  new Order(3) });
collection.Add("key2", new Order(4));

score 0 · Answer 5 · answered Apr 08 '14 at 12:34

0

Try this

    Dictionary<string,order[] order> dict = new Dictionary<string,order[] order>();

    how to access :

    order[] orderArray = dict["key1"];
    order order1 = orderArray[1] ;
    order order2 = orderArray[2] ;

    and goes on...

answered Apr 08 '14 at 12:34

shujaat siddiqui

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Dictionary with multiple values for each key?

5 Answers5