Dictionary Generic Collection In C#

Generic Collections:

• Are Type Safe.
• Variable length (Auto Resizing)

ArrayList VS HashTable

C# – Dictionary

• Now we want to create a collection in which we don’t want to access elements through index.
• We want to store data in key value format where keys are user-defined.
• We want to insert same type of data in a collection.

DICTIONARY<TKey, TValue>

“active”: ”ready to engage in physically energetic pursuits”,
“amazing”: “causing great surprise or wonder”,
“honest”: “free of deceit, truthful and sincere”,
“patriotic”: “expressing devotion to and vigorous support for 				   one's country.”,
“quarantine”: “place of isolation”

• In C#, Dictionary is a generic collection which is generally used to store key/value pairs.
• The working of Dictionary is quite similar to the non-generic hashtable.
• The advantage of Dictionary is, it is generic type.
• Dictionary is defined under System.Collection.Generic namespace.
• It is dynamic in nature means the size of the dictionary is grows according to the need.
• The Dictionary collection in C# is same as English dictionary.
• English dictionary is a collection of words and their definitions, often listed alphabetically in one or more specific languages.
• In the same way, the Dictionary in C# is a collection of Keys and Values, where key is like word and value is like definition.
• The Dictionary class is a generic collection class in the System.Collection.Generics namespace.
• TKey denotes the type of key and TValue is the type of TValue.

Important Properties Of Dictionary

• Count: Gets the total number of elements exists in the Dictionary.
• Keys: Returns collection of keys of Dictionary.
• Values: Returns collection of values in Dictionary.

Important METHODS Of Dictionary

• Add Adds an item to the Dictionary collection,Add key- value pairs in Dictionary collection.
• Remove Removes the element with the specified key.
• ContainsKey Checks whether the specified key exists in Dictionary.
• ContainsValue Checks whether the specified key exists in Dictionary.
• Clear Removes all the elements from Dictionary.
• TryGetValue Returns true and assigns the value with specified key, if key does not exists then return false.

Important Points

• In Dictionary, the key cannot be null, but value can be.
• In Dictionary, key must be unique. Duplicate keys are not allowed if you try to use duplicate key then compiler will throw an exception.
• In Dictionary, you can only store same types of elements.
• The capacity of a Dictionary is the number of elements that Dictionary can hold.

Source Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DictionaryGenericCollection
{
    class Program
    {
        static void Main(string[] args)
        {
            //Dictionary<string, string> myDict = new Dictionary<string, string>();
            //myDict.Add("active", "ready to engage in physically energetic pursuits");
            //myDict.Add("amazing", "causing great surprise or wonder");
            //myDict.Add("honest", "free of deceit, truthful and sincere");
            //myDict.Add("patriotic", "expressing devotion to and vigorous support for one's country.");
            //myDict.Add("quarantine", "place of isolation");

            //Employee emp1 = new Employee()
            //{
            //    id = 111,
            //    name = "Ali",
            //    designation = "Manager",
            //    salary = 15000
            //};

            //Employee emp2 = new Employee()
            //{
            //    id = 222,
            //    name = "Asad",
            //    designation = "Assistant",
            //    salary = 12000
            //};

            //Employee emp3 = new Employee()
            //{
            //    id = 333,
            //    name = "Zain",
            //    designation = "Operator",
            //    salary = 8000
            //};

            //Dictionary<int, Employee> myEmployees = new Dictionary<int, Employee>();
            //myEmployees.Add(emp1.id, emp1);
            //myEmployees.Add(emp2.id, emp2);
            //myEmployees.Add(emp3.id, emp3);

            //Console.WriteLine(myEmployees.Count(emp => emp.Value.name.StartsWith("B")));

            //Console.WriteLine(myDict.Count());

            //Dictionary<int, string> myDict2 = new Dictionary<int, string>();
            //myDict2.Add(1, "Adil");

            //Console.WriteLine(myDict["active"]);

            Dictionary<string, string> myDict = new Dictionary<string, string>();
            myDict.Add("active", "ready to engage in physically energetic pursuits");
            myDict.Add("amazing", "causing great surprise or wonder");
            myDict.Add("honest", "free of deceit, truthful and sincere");
            myDict.Add("patriotic", "expressing devotion to and vigorous support for one's country.");
            myDict.Add("quarantine", "place of isolation");



            if (myDict.ContainsKey("quarantine"))
            {
                Console.WriteLine("Key Found");
            }
            else
            {
                Console.WriteLine("Key not Found");
            }




            //string value;
            //myDict.TryGetValue("honest", out value);
            //Console.WriteLine(value);

            //foreach (KeyValuePair<string, string> item in myDict)
            //{
            //    Console.WriteLine("Key is: " + item.Key + " Value is: " + item.Value);
            //}

            //myDict.Clear();
            //Console.WriteLine("-----------------------");
            //foreach (KeyValuePair<string, string> item in myDict)
            //{
            //    Console.WriteLine("Key is: " + item.Key + " Value is: " + item.Value);
            //}

            //Console.WriteLine(myDict.ContainsValue("bmnbmnbmnb"));

            //if(myDict.ContainsKey("quarantine"))
            //{
            //    Console.WriteLine("Key Found");
            //}
            //else
            //{
            //    Console.WriteLine("Key Not Found");
            //}

            //Console.WriteLine(myDict.ContainsKey("Adil"));

            //foreach (KeyValuePair<string, string> item in myDict)
            //{
            //    Console.WriteLine("Key is: " + item.Key + " Value is: " + item.Value);
            //}

            //myDict.Remove("quarantine");
            //Console.WriteLine("-----------------------");
            //foreach (KeyValuePair<string, string> item in myDict)
            //{
            //    Console.WriteLine("Key is: " + item.Key + " Value is: " + item.Value);
            //}

            //foreach (string key in myDict.Keys)
            //{
            //    Console.WriteLine(key);
            //}

            //foreach (string value in myDict.Values)
            //{
            //    Console.WriteLine(value);
            //}

            Console.ReadLine();
        }
    }
}