How to insert values into C# Dictionary on instantiation?

Question

Does anyone know if there is a way I can insert values into a C# Dictionary when I create it? I can, but don't want to, do dict.Add(int, "string") for each item if there is something more efficient like:

Dictionary<int, string>(){(0, "string"),(1,"string2"),(2,"string3")};

possible duplicate of [Can I use a collection initializer for Dictionary entries?](http://stackoverflow.com/questions/495038/can-i-use-a-collection-initializer-for-dictionarytkey-tvalue-entries) — Chris Moschini, Sep 27 '13 at 20:08

Daniel Earwicker · Accepted Answer · 2013-08-12T10:16:39.620

217

There's whole page about how to do that here:

http://msdn.microsoft.com/en-us/library/bb531208.aspx

Example:

In the following code example, a Dictionary<TKey, TValue> is initialized with instances of type StudentName:

var students = new Dictionary<int, StudentName>()
{
    { 111, new StudentName {FirstName="Sachin", LastName="Karnik", ID=211}},
    { 112, new StudentName {FirstName="Dina", LastName="Salimzianova", ID=317}},
    { 113, new StudentName {FirstName="Andy", LastName="Ruth", ID=198}}
};

edited Aug 12 '13 at 10:16

answered Jun 24 '09 at 16:57

Daniel Earwicker

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3

This only works on .NET 3.5 compiler though... just keep that in mind. – Adrian Godong Jun 24 '09 at 16:59
@kd7iwp - no problem, part of the function of this site is so that alternative search terms can get routed to something useful. – Daniel Earwicker Jun 24 '09 at 17:13
Yeah, that's pretty much a given with Microsoft. They have been pretty committed to backward-compatibility over the years. – PRMan Sep 19 '14 at 21:20

score 49 · Answer 2 · answered Jun 24 '09 at 16:59

49

Dictionary<int, string> dictionary = new Dictionary<int, string> { 
   { 0, "string" }, 
   { 1, "string2" }, 
   { 2, "string3" } };

answered Jun 24 '09 at 16:59

Timothy Carter

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H H · Answer 3 · 2022-06-15T06:16:46.983

14

You were almost there:

var dict = new Dictionary<int, string>()
{ 
   {0, "string"}, 
   {1, "string2"},
   {2, "string3"}
};

edited Jun 15 '22 at 06:16

answered Jun 24 '09 at 16:59

H H

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score 11 · Answer 4 · answered Mar 23 '12 at 17:04

You can also use Lambda expressions to insert any Key Value pairs from any other IEnumerable object. Key and value can be any type you want.

Dictionary<int, string> newDictionary = 
                 SomeList.ToDictionary(k => k.ID, v => v.Name);

I find that much simpler since you use the IEnumerable objects everywhere in .NET

Hope that helps!!!

Tad.

score 9 · Answer 5 · answered Aug 05 '15 at 08:53

Just so you know as of C# 6 you can now initialize it as follows

var students = new Dictionary<int, StudentName>()
{
    [111] = new StudentName {FirstName="Sachin", LastName="Karnik", ID=211},
    [112] = new StudentName {FirstName="Dina", LastName="Salimzianova", ID=317},
    [113] = new StudentName {FirstName="Andy", LastName="Ruth", ID=198}
};

Much cleaner :)

score 7 · Answer 6 · answered Jun 24 '09 at 16:59

7

You can instantiate a dictionary and add items into it like this:

var dictionary = new Dictionary<int, string>
    {
        {0, "string"},
        {1, "string2"},
        {2, "string3"}
    };

answered Jun 24 '09 at 16:59

Joseph

25,330
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score -1 · Answer 7 · answered Mar 15 '15 at 19:00

-1

Hope it will work perfectly.

Dictionary<string, double> D =new Dictionary<string, double>(); D.Add("String", 17.00);

answered Mar 15 '15 at 19:00

Hi, welcome to SO! The person who originally asked this question specifically said that they don't want to do the `.Add(int, "string")` method of adding values to a dictionary. Sorry but this doesn't answer the question. – Kezz Mar 15 '15 at 19:22

score -2 · Answer 8 · answered Aug 15 '18 at 17:33

This isn't generally recommended but in times of uncertain crises you can use

Dictionary<string, object> jsonMock = new Dictionary<string, object>() { { "object a", objA }, { "object b", objB } };

// example of unserializing
ClassForObjectA anotherObjA = null;
if(jsonMock.Contains("object a")) {
    anotherObjA = (ClassForObjA)jsonMock["object a"];
}

How to insert values into C# Dictionary on instantiation?

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