Defining new Dictionary members methods C#

Question

I want to define a new member method for Dictionary as it already built in member methods e.g. Add(), Clear(), ContainsKey() etc.

That newly added member method should return all the keyvaluepairs in form of a Set as we can return map.entrySet() to Set in Java.

Can existing methods for dictionary be overridden to achieve this ?

Out of curiosity, why do you want it? What are you doing that getting a map.entrySet() equivalent will help you solve that problem? — Scott Chamberlain, Jun 04 '16 at 17:37

Federico Dipuma · Accepted Answer · 2016-06-04T18:30:43.003

2

You could create an extension method:

using System;
using System.Collections.Generic;
using System.Linq;

public static class DictionaryExtensions {
    public static HashSet<KeyValuePair<TKey, TValue>> ToSet<TKey, TValue>(this Dictionary<TKey, TValue> dict) {
        return new HashSet<KeyValuePair<TKey, TValue>>(dict.ToList());
    }
}

Info about extension methods: https://msdn.microsoft.com/en-us/library/bb383977(v=vs.110).aspx

edited Jun 04 '16 at 18:30

answered Jun 04 '16 at 11:02

Federico Dipuma

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where we have to declare this class and method? – maliks Jun 04 '16 at 11:05
Check the link added to the answer. You may add this class to any project where you need to use ToSet() – Federico Dipuma Jun 04 '16 at 11:06
do we need to declare as DictionaryExtension {...} as To use KVP inside ? – maliks Jun 04 '16 at 11:14
It's a static class, there is no need to create a generic one. Please read more about what extension methods are and how to use them inside the link I provided. It's truly a board topic. – Federico Dipuma Jun 04 '16 at 11:16
But when I declared it inside my class, it gives error due to `KVP` as type or namespace couldn't be found – maliks Jun 04 '16 at 11:17
I'm sorry but I do not understand your problem. You have to create a new class in a new file and add the correct using statements to it (e.g. System.Collections.Generics). – Federico Dipuma Jun 04 '16 at 11:23
You may choose the name you like, but the class must be static. – Federico Dipuma Jun 04 '16 at 11:27
I have declared as: `public static class MyExtensions { public static HashSet> ToSet(this Dictionary _dict) { return new HashSet>(_dict.ToList()); } }` But still type or namespace couldn't be found error – maliks Jun 04 '16 at 11:30
Just by adding `MyExtensions` then no error, why is it so? – maliks Jun 04 '16 at 11:38
Comments are not a chat, please never create extended discussion here. By the way, is not , but . – Federico Dipuma Jun 04 '16 at 12:02
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/113815/discussion-between-taufel-and-federico-dipuma). – maliks Jun 04 '16 at 15:45
Please check again the answer, I've updated it. It should work out of the box. – Federico Dipuma Jun 04 '16 at 18:31

score 0 · Answer 2 · answered Jun 04 '16 at 10:59

0

I'm aware it's not a set, but by using Linq you can get a list of key value pairs like so:

Dictionary<string, string> dictionary = new Dictionary<string, string>();
List<KeyValuePair<string, string>> keyValuePairs = dictionary.ToList();

answered Jun 04 '16 at 10:59

Richard

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score 0 · Answer 3 · answered Jun 04 '16 at 12:52

0

Just in case it helps, you can access KeyValue pair of the Dictionary like this :

// Example dictionary
var dic = new Dictionary<int, string>{{1, "a"}};

foreach (var item in dic)
{
    Console.WriteLine(string.Format("key : {0}, Value : {1}", item.Key, item.Value));
}

answered Jun 04 '16 at 12:52

Edgars Pivovarenoks

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I want to have a method which return all KeyValuePair of the Dictionary which I can call as an extension method – maliks Jun 04 '16 at 15:44

Defining new Dictionary members methods C#

3 Answers3