How do I merge two dictionaries?

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I need help finding out how i can merge 2 dictionaries together, creating one.

i have this code so far:

using System;
using System.Collections.Generic;

namespace merging_dictionaries
{
    class Program
    {
        static void Main(string[] args)
        {
            Dictionary<string, string> dict = new Dictionary<string, string>
            {
                { "WA", "Western Autralia" },
                { "NSW", "New South Wales" },
                { "SA", "South Australia" },
                { "Q", "Queensland" },
                { "V", "Victoria" },
                { "T", "Tasmania" }
            };

            Dictionary<string, string> otherdict = new Dictionary<string, string>
            {
                { "1", "Adclarkia dawsonensis" },
                { "2", "Advena campbellii " },
                { "3", "Discocharopa vigens" },
                { "4", "Hyridella glenelgensis" },
                { "5", "Mathewsoconcha grayi ms" },
                { "6", "Mathewsoconcha phillipii" }//these names are of endangered australian molusks, why not?
            };

            MergeDictionary(dict, otherdict);
        }

        public static Dictionary<string, string> MergeDictionary(Dictionary<string, string> dict1, Dictionary<string, string> dict2)
        {
            foreach (var thing in dict1)
            {
                dict2.Add(thing.Key);//make it do something with Add. 
                dict2.Add(thing.Value);//here i am trying to make it add the key and the value, but i have no idea how. 
            }
        }
    }
}

I can't make this work as intended, if at all.

Please help me fix it.

Thank you.

What I have tried:

I ave tried different ways of putting the dictionaries together with no success.

I have tried different ways of adding the keys and values, one at a time or all together, to no avail.

Posted 12-May-19 1:02am

i like food

Updated 12-May-19 16:25pm

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Comments

[no name] 12-May-19 8:50am

Check also this...
How do I combine two dictionaries[^]

and this....
c# - Combine multiple dictionaries into a single dictionary - Stack Overflow[^]

Maciej Los 12-May-19 9:06am

My virtual 5!

BillWoodruff 12-May-19 22:15pm

virtual +5

3 solutions

Solution 3

I needed something a little different that lets me specify ... in the case of duplicate Keys ... which Dictionary is the source of the value taken from the duplicate KeyValuePairs used in the merged output:

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

namespace WhatEver
{
    public static class DictionaryExtensions
    {
        public static Dictionary<TKey, TValue> Merge<TKey, TValue>(this Dictionary<TKey, TValue> dict1,
            Dictionary<TKey, TValue> dict2, bool useDupValueFromDict1 = true)
        {
            if (dict1.Equals(dict2)) throw new ArgumentException("duplicate dictionaries");

            if (dict1 == null) throw new ArgumentException("dictionary 1 is null");

            if (dict2 == null) throw new ArgumentException("dictionary 2 is null");

            if (dict1.Count == 0) throw new ArgumentException("dictionary 1 has no items");

            if (dict2.Count == 0) throw new ArgumentException("dictionary 2 has no items");

            Dictionary<TKey, TValue> result;
            IEnumerable<KeyValuePair<TKey, TValue>> nondups;

            if (useDupValueFromDict1)
            {
                result = dict1;
                nondups = dict2.Where(kvp => !dict1.ContainsKey(kvp.Key));

            }
            else
            {
                result = dict2;
                nondups = dict1.Where(kvp => !dict2.ContainsKey(kvp.Key));
            }

            return result.Union(nondups).ToDictionary(kvp1 => kvp1.Key, kvp1 => kvp1.Value);
        }
    }
}

Another variation (not shown here) lets you specify a comparison Func that will select which of the duplicate KeyValuePairs is used.

Posted 12-May-19 16:25pm

BillWoodruff

Updated 12-May-19 22:47pm

v2

Comments

Maciej Los 13-May-19 2:24am

You did what i mentioned in my answer.
5ed!

BillWoodruff 13-May-19 3:00am

I am always walking in the footprints of giants :) My motivation for writing this, a few years ago, was a need to control which Dictionary's values were used in the case of duplicate Keys.

[no name] 13-May-19 12:02pm

A 5 for this.

BillWoodruff 13-May-19 21:23pm

thank you !

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Maciej Los · Accepted Answer · 2019-05-12T02:55:00

Solution 2

Check this thread: dictionary - Merging dictionaries in C# - Stack Overflow[^]. There's few ways to merge/combine dictionaries.

I'd improve them by adding line of code which will check if particular Key exists.

Good luck!

Posted 12-May-19 2:55am

Maciej Los

Updated 12-May-19 3:04am

v2

Comments

[no name] 12-May-19 9:40am

A 5

Maciej Los 12-May-19 9:48am

Thank you, Bruno.

BillWoodruff 13-May-19 3:00am

+5

Maciej Los 13-May-19 3:30am

Thank you, Bill.

Thomas Daniels · Accepted Answer · 2019-05-12T02:27:00

Solution 1

You're using Add wrongly, you have to use it like this:

C#

dict2.Add(thing.Key, thing.Value);

Posted 12-May-19 2:27am

Thomas Daniels

Comments

Maciej Los 12-May-19 9:04am

5ed!

[no name] 12-May-19 9:40am

A 5