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Quick CheatSheet C# HashTables

Note - it seems Dictionaries are a little quicker and a little less memory intensive than HashTables. This is because we kind of "FIX" the type when we create the Dictionary - eg

Dictionary<string, string> myDict = new Dictionary<string, string>();

using System.Collections;

public class Program
{
    //Note - it seems Dictionaries are a little quicker and a little less memory intensive than HashTables.
    //This is because the kind "FIX" the type when we create the Dictionary - eg 
    //Dictionary<string, string> myDict = new Dictionary<string, string>();

    static void Main()
    {
        //Syntax 1 for creating HashTable
        Hashtable cities = new Hashtable();
        cities.Add("UK", "London, Manchester, Preston");
        cities.Add("USA", "Michigan, Las Vegas, Reno");
        cities.Add("France", "Paris, Rennes, Le Mons");

        //Building a string for showing
        foreach(DictionaryEntry entry in cities)
        {
            Console.WriteLine(entry.Key + "=" + entry.Value);
        }

        //Syntax 2 for creating HashTable
        Hashtable city = new Hashtable()
        {
            { "UK", "London, Manchester, Preston" },
            { "USA", "Michigan, Las Vegas, Reno" },
            { "France", "Paris, Rennes, Le Mons" }
        };

        //String built using interpolation
        foreach (DictionaryEntry entry in city)
        {
            Console.WriteLine("The key is {0}, the value is {1}", entry.Key, entry.Value);
        }

        //A dictionary drops straight into a Hashtable
        Dictionary<string, string> myDict = new Dictionary<string, string>();
        myDict.Add("Honda", "CB300R, CB125F");
        myDict.Add("Kawasaki", "Z250SL, Z400");
        myDict.Add("Yamaha", "MT03, MT07");

        Hashtable bikes = new Hashtable(myDict);

        foreach(DictionaryEntry entry in bikes)
        {
            Console.WriteLine("Make {0}, Models {1}", entry.Key, entry.Value);
        }

        //Get one item
        string qwe = bikes["Honda"].ToString();
        Console.WriteLine(qwe);

        //Update
        bikes["Honda"] = "CB500X, CB750";
        Console.WriteLine(bikes["Honda"].ToString());

        //Remove
        bikes.Remove("Yamaha");

        foreach (DictionaryEntry entry in bikes)
        {
            Console.WriteLine("Make {0}, Models {1}", entry.Key, entry.Value);
        }

        //check it exists
        if (bikes.ContainsKey("Honda"))
        {
            Console.WriteLine("We found Honda");
        }
        if (bikes.Contains("Honda"))
        {
            Console.WriteLine("We found Honda again");
        }

        //remove everything
        bikes.Clear();
    }
}
 

Reader's Comments

Fred said :-
Ta
04/12//2023 15:27:14 UTC

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