How to Convert KeyValuePair to Dictionary in C#

Question

How does one convert a KeyValuePair to a Dictionary, given that ToDictionary is not available in C#?

Isn't it? Well you could just use `var dict = new Dictionary()` then `dict.Add(kvp.Key, kvp.Value)` — Charleh, Sep 23 '13 at 09:02
It is a duplicate, Robin incorrectly says C# has no ToDictionary — doctorlove, Sep 23 '13 at 09:05
@JasonEvans Strictly, it's not a dupe - he is asking how to convert a KeyValuePair, not a List[KeyValuePair]. Of course, this does demand the question "Why does he want to do this"?!! — RB., Sep 23 '13 at 09:05
@doctorlove KeyValuePair does not have a ToDictionary method - it's on IEnumerable, and the question (as written) is not talking about an IEnumerable. — RB., Sep 23 '13 at 09:05

jwg · Accepted Answer · 2013-09-23T09:18:14.377

172

var dictionary = new Dictionary<string, object> { { kvp.Key, kvp.Value } };

ToDictionary does exist in C# (edit: not the same ToDictionary you were thinking of) and can be used like this:

var list = new List<KeyValuePair<string, object>>{kvp};
var dictionary = list.ToDictionary(x => x.Key, x => x.Value);

Here list could be a List or other IEnumerable of anything. The first lambda shows how to extract the key from a list item, and the second shows how to extract the value. In this case they are both trivial.

edited Sep 23 '13 at 09:18

answered Sep 23 '13 at 09:11

jwg

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how can I do that with C# 2.0 – rikush Nov 20 '18 at 12:41
Please add note that you need to use System.Linq – Ibrahim Jul 01 '19 at 23:59

score 8 · Answer 2 · answered Sep 23 '13 at 09:12

8

If I understand correctly you can do it as follows:

new[] { keyValuePair }.ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

answered Sep 23 '13 at 09:12

BartoszKP

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score 4 · Answer 3 · answered Jul 23 '20 at 15:52

Use System.Linq.Enumerable.ToDictionary() extension method to convert a collection of one or more KeyValuePairs

Dictionary<string,string> result = new[] {  
    new KeyValuePair ("Key1", "Value1"),
    new KeyValuePair ("Key2", "Value2") 
}.ToDictionary(pair => pair.Key, pair => pair.Value);

score 1 · Answer 4 · edited Jun 30 '17 at 13:32

1

Create a collection of KeyValuePair and make sure System.Linq is imported in a using statement.

Then you will be able to see the .ToDictionary() extension method.

public IList<KeyValuePair<string, object>> MyDictionary { get; set; }

edited Jun 30 '17 at 13:32

g t

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answered Sep 23 '13 at 09:09

JSJ

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score 1 · Answer 5 · answered Sep 23 '13 at 09:16

Alternatively (if you can't use Linq.. although I'm curious why..).. implement ToDictionary yourself...

public static Dictionary<TKey, TElement> ToDictionary<TSource, TKey, TElement>(IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector) {
    if (source == null)
    {
        throw new ArgumentNullException("source");
    }
    if (keySelector == null) {
        throw new ArgumentNullException("keySelector");
    }
    if (elementSelector == null) {
        throw new ArgumentNullException("elementSelector");
    }

    var dictionary = new Dictionary<TKey, TElement>();
    foreach (TSource current in source) {
        dictionary.Add(keySelector(current), elementSelector(current));
    }
    return dictionary;
}

Example usage:

var kvpList = new List<KeyValuePair<int, string>>(){
    new KeyValuePair<int, string>(1, "Item 1"),
    new KeyValuePair<int, string>(2, "Item 2"),
};

var dict = ToDictionary(kvpList, x => x.Key, x => x.Value);

score 1 · Answer 6 · answered Mar 24 '22 at 16:25

1

Upgrade to .net 5 or higher and pass them to the constructor:

    var x = new Dictionary<string, string>(new[] { new KeyValuePair<string, string>("key1", "val1"), new KeyValuePair<string, string>("key2", "val2") });

answered Mar 24 '22 at 16:25

Wolfgang Grinfeld

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br1 · Answer 7 · 2016-06-07T03:27:25.183

0

Implement it yourself as an extension method.

public static class MyExtensions
{

    public static Dictionary<T1,T2> ToDictionary<T1, T2>(this KeyValuePair<T1, T2> kvp)
    {
      var dict = new Dictionary<T1, T2>();
      dict.Add(kvp.Key, kvp.Value);
      return dict;
    }

}

see this in action: https://dotnetfiddle.net/Ka54t7

edited Jun 07 '16 at 03:27

answered Sep 23 '13 at 09:11

br1

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It may not be obvious to some people that the above code cannot be used as-is: One would need to substitute the actual type for T1 and T2, such as string and object... – Jazimov Jun 03 '16 at 23:19
Oh no, I just forgot one bit – br1 Jun 07 '16 at 03:22
1

Jazimov. T1 & T2 are generic type references. You would not substitute them. They are inferred by the KeyValuePair instance being extended. With that said, while this literally answers the question, it isn't useful because you're creating a dictionary collection with only 1 item in its collection. It would be better to extend an IEnumerable of KeyValuePairs, like an array or List. – Antony Booth Jul 23 '20 at 15:44

How to Convert KeyValuePair to Dictionary in C#

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