C# 13 - Collections - Todo List

1. Create a new console project. 
2. Edit the Program.cs to look like as shown below.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
 
namespace TodoList
{
    class Program
    {
        private static List<string> todolist = new List<string>();
 
        static void Main(string[] args)
        {            
            string menuOption;
            bool exitApplication = false;
 
            do
            {
                Console.WriteLine("===========================");
                Console.WriteLine("Welcome to your Todo List.");
                Console.WriteLine("===========================");                
                Console.WriteLine("[1] Show Todo List");
                Console.WriteLine("[2] Add a new Todo");
                Console.WriteLine("[3] Delete a Todo");
                Console.WriteLine("[4] Exit");
                Console.Write("What do you want to do? ");
                menuOption = Console.ReadLine();
 
                switch(menuOption)
                {
                    case "1":
                        Console.WriteLine("---------------------------");
                        ShowTodoList();
                        Console.WriteLine("---------------------------");
                        break;
                    case "2":
                        Console.WriteLine("---------------------------");
                        AddNewTodo();
                        Console.WriteLine("---------------------------");
                        break;
                    case "3":
                        Console.WriteLine("---------------------------");
                        DeleteATodo();
                        Console.WriteLine("---------------------------");
                        break;
                    case "4":
                        Console.WriteLine("---------------------------");
                        Console.WriteLine("Exit");
                        Console.WriteLine("---------------------------");
                        exitApplication = true;
                        break;
                    default:
                        Console.WriteLine("Invalid option");
                        break;
                }                
 
            } while (!exitApplication);
        }
 

        private static void DeleteATodo()
        {
            string todoNumberInput;
            int todoNumber;
 
            ShowTodoList();
            Console.Write("What Todo do you want to delete? ");
            todoNumberInput = Console.ReadLine();
 
            if (Int32.TryParse(todoNumberInput, out todoNumber))
            {
                if (todoNumber > todolist.Count)
                    Console.WriteLine("Todo does not exist.");
                else
                    todolist.RemoveAt(todoNumber);
            }
            else
            {
                Console.WriteLine("Input must be a number");
            }
        }

 
        private static void AddNewTodo()
        {
            string newTodo;
 
            Console.Write("What will you be doing? ");
            newTodo = Console.ReadLine();
            todolist.Add(newTodo);
        }
 
        private static void ShowTodoList()
        {
            int todoNumber = 1;
 
            if (todolist.Count == 0)
            {
                Console.WriteLine("Your Todo list is empty");
            }
            else
            {
                foreach (string todo in todolist)
                {
                    Console.WriteLine("[" + todoNumber + "] " + todo);
                    todoNumber++;
                }
            }
        }
        
    }
}

3. Press F5 to run and see the results.

4. Thank you.

Learn more about Collections.

Collection Classes
C# List and ArrayList
Choosing the right collection class

C# 12 - Multidimensional Arrays - Multiplication Table

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1. Create a new console project.

2. Edit the Program.cs inside static void Main(string[] args) file as shown below.

static void Main(string[] args)

        {
            int[,] multiplicationTable = new int[11,11];
 
            for (int i = 1; i < 11; i++)
                for (int x = 1; x < 11; x++)
                    multiplicationTable[i, x] = i * x;
 
            Console.Write("x".PadRight(3) + "|");
            for (int i = 1; i < 11; i++)
            {
                Console.Write(i.ToString().PadRight(3) + "|");
            }
            Console.Write("\n");
            Console.WriteLine("--------------------------------------------");
 
            for (int i = 1; i < 11; i++)
            {
                Console.Write(i.ToString().PadRight(3) + "|");
                for (int x = 1; x < 11; x++)
                {
                    Console.Write(multiplicationTable[i, x].ToString().PadRight(3) + "|");
                }
                Console.Write("\n");
                Console.WriteLine("--------------------------------------------");
            }
 
            Console.ReadLine();
       }       

3. Press F5 to run and see the results.

4. Thank you.

Rectangular array is another type of array that allows you to define a table like array that has a row and column definition.

Syntax:

type[,] = new type[row,column];

type – can be any data type

row – is the number of rows for your table

column – is the number of columns for your table

e.g.

                int[,] mytable = new int[10, 5];

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C# 11 - Arrays

An array of sorts.

1. Create a new console project.
2. Edit the Program.cs inside static void Main(string[] args) file as shown below.

static void Main(string[] args)
{
     //declaring and initializing an array
     string[] theAvengers = new string[5];
     theAvengers[0] = "Iron Man";
     theAvengers[1] = "Thor";
     theAvengers[2] = "Captain America";
     theAvengers[3] = "Hawkeye";
     theAvengers[4] = "Hulk";
 
     Console.WriteLine("The Avengers!");
     Console.WriteLine("-------------------------");
     //loop through an array to access or modify its contents
     for (int i = 0; i < 5; i++)
     {
         Console.WriteLine(theAvengers[i]);
     }
 
     //another way of declaring and initializing an array
     //also another way is

    //string[] uncannyXMen = new string[] { "Wolverine", "Prof. X", "Cyclops", "Storm", "Beast" };

     string[] uncannyXMen = { "Wolverine", "Prof. X", "Cyclops", "Storm", "Beast" };
             
     Console.WriteLine("\nThe X-Men!");
     Console.WriteLine("-------------------------");

     //loop through an array to access in contents
     for (int i = 0; i < uncannyXMen.Length; i++)
     {
          Console.WriteLine(uncannyXMen[i]);
     }
 

     Console.WriteLine("Press any key to continue...");
     Console.ReadLine();
}

3. Press F5 to run and see the results.

4. Thank you.

Declaring an array allows you to store multiple items of a specific type. It syntax is:

type[] arrayName;

To learn more about arrays check these resources.

Arrays(C# Programming Guide)

Arrays tutorial

C# 10 - do-while-loop statement

1. Create a new console project.
2. Edit the Program.cs inside static void Main(string[] args) file as shown below.

   static void Main(string[] args)

        {

            int counter = 0;            

            while (counter < 10)

            {

                Console.WriteLine("Hello World from a while loop.");

                counter++;

            }

            Console.WriteLine("Press any key to continue...");

            Console.ReadLine();

            }

3. Press F5 to run and see the results.

5. Thank you.

The do- while-loop statement is used perform a piece of code multiple times as long as the condition set is evaluated to true. It executes code at least once. Its syntax is:

do

{

                //code to execute

}

while(<condition>);

C# 9 - while-loop statement

1. Create a new console project.
2. Edit the Program.cs inside static void Main(string[] args) file as shown below.

    class Program
    {
        static void Main(string[] args)
        {
            int counter = 0;
            
            while (counter < 10)
            {
                Console.WriteLine("Hello World from a while loop.");
                counter++;
            }
 
            Console.WriteLine("Press any key to continue...");
            Console.ReadLine();
        }
    }

3. Press F5 to run and see the results.

4. Thank you.


The while-loop statement is used perform a piece of code multiple times as long as the condition set is evaluated to true. Its syntax is:

while(<condition>)
{
    //code to execute
}

C# 8 - For loop statement

1. Create a new console project.
2. Edit the Program.cs inside static void Main(string[] args) file as shown below.

        static void Main(string[] args)
        {
            for (int i = 0; i < 10; i++)
            {
                Console.WriteLine("Hello World!");
            }
            
            Console.WriteLine("Press any key to continue.....");
            Console.ReadLine();
        }

3. Press F5 to run and see the results.

4. Thank you.

The for-loop statement is used perform a piece of code multiple times as long as the condition set is evaluated to true. Its syntax is:

for(<initialization>;<condition>;<incrementation/decrementation>)

{

                //code to execute

}

C# 7 - Switch statement

1. Create a new console project.
2. Edit the Program.cs file as shown below.

 static void Main(string[] args)
        {
            Console.WriteLine("What is your most favorite sweet stuff?");
            Console.WriteLine("[1]Chocolate");
            Console.WriteLine("[2]Candy");
            Console.WriteLine("[3]Lollipop");
            Console.WriteLine("[4]Sugar");
            Console.WriteLine("[5]Honey");
            Console.WriteLine("[6]Cake");
            Console.Write("Enter your choice: ");
            string choice = Console.ReadLine();
 
            switch (choice)
            {
                case "1":
                    Console.WriteLine("Chocolate, chocolate, chocolate!");
                    break;
                case "2":
                    Console.WriteLine("Candy, candy, candy!");
                    break;
                case "3":
                    Console.WriteLine("Lollipop, lollipop, lollipop!");
                    break;
                case "4":
                    Console.WriteLine("Sugar, sugar, sugar!");
                    break;
                case "5":
                    Console.WriteLine("Honey, honey, honey!");
                    break;
                case "6":
                    Console.WriteLine("Cake, cake, cake!");
                    break;
                default:
                    Console.WriteLine("Hmmm, I don't know what you're favorite is.");
                    break;
            }
            
            Console.WriteLine("Press any key to continue.....");
            Console.ReadLine();
 
        }

3. Press F5 to run and see the results.

4. Thank you.

The switch statement is used to add condition to a piece of code. Its syntax is:

switch(<expression>)

                case <expression result>:

                                //code to execute

                                break;

                case <expression result>:

                                //code to execute

                                Break;

                .

                .

                .

                default:

                                //code to execute if there are no matching case

                                break;

expression – could be anything that would result in a value that would get evaluated in each of the cases.