Dictionary in C#

DevSniper
Published : 24 February 2024

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Namespace :- System.Collections.Generic

Assembly :- System.Collections.dll

Signature :-

public class Dictionary<TKey,TValue> :

System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>,
System.Collections.Generic.IDictionary<TKey,TValue>,
System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey,TValue>>, 
System.Collections.Generic.IReadOnlyCollection<System.Collections.Generic.KeyValuePair<TKey,TValue>>, 
System.Collections.Generic.IReadOnlyDictionary<TKey,TValue>, 
System.Collections.IDictionary, 
System.Runtime.Serialization.IDeserializationCallback, 
System.Runtime.Serialization.ISerializable

In C#, Dictionary is a generic Collection which is define under System.Collections.Generic namespace. It is used to store data in the form of key , value pairs (Dictionary<TKey,TValue>).

-: DICTIONARY CONSTRUCTORS :-

There are 7 constructors in c# Dictionary.

1. Dictionary<TKey, TValue>()

2. Dictionary<TKey,TValue>(IDictionary<TKey,TValue>)

3. Dictionary<TKey,TValue>(IDictionary<TKey,TValue>, IEqualityComparer<TKey>)

4. Dictionary<TKey,TValue>(IEqualityComparer<TKey>)

5. Dictionary<TKey,TValue>(Int32)

6. Dictionary<TKey,TValue>(Int32, IEqualityComparer<TKey>)

7. Dictionary<TKey,TValue>(SerializationInfo, StreamingContext)

-: CREATING A DICTIONARY AND ADDING ELEMENTS :-

1. initialize the dictionary with initial values

using System.IO;
using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary < string,string> dict = new Dictionary<string,string> {
            {"language","C#"},
            {"topic","Dictionary"},
            {"label","Beginner"}
        };
        Console.WriteLine("We are learning "+dict["language"]+" "+dict["topic"] +" and level : "+dict["label"]);
    }
}

2. Direct Assign to add new element in dictionary

using System.IO;
using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary < string,string> dict=new Dictionary<string,string>();
        dict["language"]="C#";
        dict["topic"]="Dictionary";
        dict["label"]="Beginner";
        Console.WriteLine("We are learning "+dict["language"]+" "+dict["topic"] +" and level : "+dict["label"]);
    }
}

3. Using Add() Method to add new element in dictionary

using System.IO;
using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary < string,string> dict=new Dictionary<string,string>();
        dict.Add("language","C#");
        dict.Add("topic","Dictionary");
        dict.Add("label","Beginner");
        Console.WriteLine("We are learning "+dict["language"]+" "+dict["topic"] +" and level : "+dict["label"]);
    }
}

IMPORTENT POINTS

Dictionary store data in the form of key , value pairs.

The value of dictionary can be null but the key can not be null.

Keys in dictionary must be unique duplicate keys are not allowed in dictionary if you try to use duplicate key , compiler will throw exception.

The size of Dictionary is Dynamic , means according to need size of dictionary increase

You cann't store dynamic type element in dictionary . only store same type element in Dictionary

Dictionary is not Thread Safe. For thread-safe you can see ConcurrentDictionary<TKey,TValue> class or ImmutableDictionary<TKey,TValue> class

Related Blogs

Dictionary Properties and Methods

How to iterate a Dictionary in C# ?