'How to Convert KeyValuePair to Dictionary in C#

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

c++sharp


Solution 1:[1]

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.

Solution 2:[2]

If I understand correctly you can do it as follows:

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

Solution 3:[3]

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);

Solution 4:[4]

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);

Solution 5:[5]

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; }

Solution 6:[6]

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

Solution 7:[7]

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") });

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1
Solution 2 BartoszKP
Solution 3 Antony Booth
Solution 4 Simon Whitehead
Solution 5 g t
Solution 6
Solution 7 Wolfgang Grinfeld

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