C# summary

Resources

C# Tutorial at w3schools

Short Cheat Sheet

Another Cheat Sheet

    static void Main(string[] args)
    {
        int num1 = 5;
        Console.WriteLine("Hello");
        Console.Write("Hello");
        Console.WriteLine("num1: " + num1);
        Console.ReadLine();
    }

Getting User Input

    Console.Write("Enter your name: ");
    string name = Console.ReadLine();
    Console.WriteLine("Hello " + name);

    int num = Conver.ToInt32("45");

    Console.Write("Enter a number: ");  // enter 3.5
    double num = Conver.ToDouble(Console.ReadLine());
    Console.WriteLine(num);

Data types

All data types

String

    string phrase = "Hello World";
    string color, name;

Char

    char grade = 'A';
    bool result = char.IsLetter(grade);

Numbers

Integral numeric

Floating-point numeric types

Whole Numbers

sbyte, short, integer, long
- sbyte - signed byte - whole numbers from -128 to 127
```
    sbyte x = 120;
```
- short - whole numbers from -32768 to 32767
```
    short x = 30000;
```
- int - whole numbers from -2,147,483,648 to 2,147,483,647
```
    int age = 30;
    int num; // default value is 0;
    
```
```
    int num = 6;
    num++;
    num--;
    
```
- long - whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
```
    long x = 5; 
```

More Numbers

The literal without suffix or with the d or D suffix is of type double
The literal with the f or F suffix is of type float
The literal with the m or M suffix is of type decimal

float

mostly used in graphics libraries

    float f = 3_000.5F;
    f = 5.4f;

double
mostly used for real world values (except money calculation)
```
    double d = 3D;
    d = 4d;
    d = 3.1415;
    
```

decimal

used for money

    decimal - high level of accuracy
    decimal myMoney = 3_000.5m;
    myMoney = 400.75M;

Calculation

    Console.WriteLine(5 + 8.1);  // result 13.1 - decimal
    Console.WriteLine(5 / 2);    // result is 2 because of math operation with integer numbers
    Console.WriteLine(5 / 2.0);  // result is 2.5 because one operand is a double

Boolean

    bool isMail = false;
    bool isMail = true;

Constants

    const double PI = 3.14159265359;
    const int weeks = 52, months = 12;

Casting

Implicit Conversion

            int num = 123;
            long bigNum = num;

            float myFloat = 13.37F;
            double myDouble = myFloat;

Explicit Conversion

    double myDouble = 13.78;
    int myInt;

    myInt = (int)myDouble;
    Console.WriteLine(myInt); // output is 13

Type Conversion

   string myStr = myDouble.ToString()

    bool isMale = true;
    string myStr = isMale.ToString(); // "true"

Strings

    string phrase = "Hello \"World";

    string phrase = "Hello " + "World";

    phrase.Length
    phrase.ToUpper()
    phrase.ToLower()
    phrase.Contains("World")    // True or False
    phrase[0]                   // First character
    phrase.IndexOf("World")     // starts at index position
    phrase.IndexOf('o')
    phrase.IndexOf('z')         // -1
    
    phrase.Substring(4)         // sub string from position 4
    phrase.Substring(4,3)       // sub string from position 4, 3 characters to take
    
    phrase.IsNullOrWhiteSpace   // returns true if the string is either null or blank, else returns false

    string fullName = string.Concat(str1, " ", str2);    

    String.Format("My name is {0}, name"); // output: my name is John

    string inputValue = string.Empty;

    string secretWord = "giraffe";
    string guess = "";

    while (guess != secretWord)
    {
        Console.Write("Enter guess: ");
        guess = Console.ReadLine();
    }
    Console.Write("You Win!");

String Interpolation - starts with $

int age = 25;
string name = "John";
Console.WriteLine($"Hello, my name is {name} and I am {age} years old.");

Output:

Hello, my name is John and I am 25 years old.

Verbatim String - starts with @

Tells the compiler to take the string literally and ignore any spaces and escape characters like \ and \n

Console.WriteLine(@"C:\Users\user1\Desktop\");

Output:
C:\Users\user1\Desktop\

    
Console.WriteLine(@"Lorem ipsum dolor sit \n amet,
    consectetur  

    
    adipisicing elit. Tempora, nihil!");

Output:

Lorem ipsum dolor sit \n amet,
                consectetur


                adipisicing elit. Tempora, nihil!

String Formatting

int age = 20;
string name = "John";
Console.WriteLine("Hello, my name is {0} and I am {1} years old.", name, age);

Output:

Hello, my name is John and I am 20 years old.

Parsing a string to integer

    string myStr = "100";
    int num = int.Parse(myStr);
    OR
    int num = Int32.Parse(myStr);
    Console.WriteLine(num); // output is 100

    string numberAsString = "120";
    int parsedValue;
    bool success = int.TryParse(numberAsString, out parsedValue);    
    if (success) 
    {
        Console.WriteLine($"Parsing successful, the number is {parsedValue}");
    } else {
        Console.WriteLine("Parsing has failed");
    }

Parsing a string to float

    string numberAsString = "0.85";             
    float num1 = float.Parse(numberAsString);
    Console.WriteLine("num1: {0}   ", num1);

    string numberAsString = "0.33";  // good for float
    float parsedValue;
    bool success = float.TryParse(numberAsString, out parsedValue);
    if (success)
    {
        Console.WriteLine($"Parsing successful, the number is {parsedValue}");
    }
    else
    {
        Console.WriteLine("Parsing has failed");
    }

Math

    Math.Round(8.3) // 8
    Math.Round(4.6) // 5
    Math.Abs(-40)   // 40
    Math.Pow(3, 2)  // 9
    Math.Sqrt(36)   // 6
    Math.Max(4, 90) // 90 
    Math.Min(4, 90) // 4

Methods

Examples

    static void Main(string[] args)
    {
        SayHi();
        Console.ReadLine();
    }

    static void SayHi() 
    {
        Console.WriteLine("Hello User");
    }

    static void Main(string[] args)
    {
        SayHi("John");
        Console.ReadLine();       
    }

    static void SayHi(string name) 
    {
        Console.WriteLine("Hello " + name);
    }

    static void Main(string[] args)
    {
            Console.WriteLine(cube(5));
        // OR
            int cubedNumber = cube(5);
            Console.WriteLine(cubedNumber);

        Console.ReadLine();       
    }

    static int cube(int num)
    {
        int result = num * num * num;
        return result;
    }

`params`

By using the params keyword, you can specify a method parameter that takes a variable number of arguments. The parameter type must be a single-dimensional array.

int minimum = MinV2(10, 15, 1, 2, 3, -8, 20); // here we pass 7 values
Console.WriteLine($"Minimum is {minimum}");
...
static int MinV2(params int[] numbers)
{
    int min = int.MaxValue;
    foreach (int num in numbers)
    {
        if (num < min)
        {
            min = num;
        }
    }
    return min;
}

If Statements

    bool isMale = true;

    if (isMale)
    {
        Console.WriteLine("You are male");
    } else 
    {
        Console.WriteLine("You are not male");
    }

    bool isMale = true;
    bool isTall = true;

    if (isMale && isTall) // and
    {
        Console.WriteLine("You are a tall male");
    } else 
    {
        Console.WriteLine("You are either not male or not tall or both");
    }

    if (isMale || isTall) // or

    if (isMale && isTall)
    {
        Console.WriteLine("You are a tall male");
    } else if (isMale && !isTall) // ! - not
    {
        ...
    } else if (!isMale && isTall)
    {
        ...
    } else {

    }

Conditions

If statement

static int GetMax(int num1, num2)
{
    int result;

    if (num1 > num2)
    {
        result = num1;
    }
    else 
    {
        result = num2;
    }

    return result;
}

if (num1 > num2)
{
    
}
else if (num1 == num2)
{
    
} else {

}

Ternary Operator

condition ? first expression if the condition is true : second expression if the condition is false;

Example:
```
    bool isEven = 6 % 2 == 0 ? true : false;
```

Switch statement

    static string GetDay(int dayNum)
    {
        string dayName;

        switch (dayName)
        {
            case 0: 
                dayName = "Sunday";
                break;

            case 1: 
                dayName = "Monday";
                break;

            case 2: 
                dayName = "Tuesday";
                break;

            case 3: 
                dayName = "Wednesday";
                break;

            case 4: 
                dayName = "Thursday";
                break;

            case 5: 
                dayName = "Friday";
                break;

            case 6: 
                dayName = "Saturday";
                break;

            default:
                dayName = "Invalid Day Number"

        }
        return dayName;
    }

Operators

Conditional (logical) operators
```
    &&
    ||
```

Comparison operators

    >
    >=
    <
    <=
    ==
    !=

Examples

    bool isLower;
    isLower = num1 < num2;  // False

    bool isEqual;
    isEqual = num1 == num2;  // True

Unary operators

!

    bool isSunny = true;
    bool res = !isSunny;

-

    int num1 = 5;
    int num2 = -num1;  // same as -1*num1

Increment operator

    int num = 0;
    num++; // takes effect on the next line
    ++num; // takes effect on the current line

Decrement operator

    int num = 0;
    num--; // takes effect on the next line
    --num; // takes effect on the current line

Math operators

    +
    -
    *   <-- multiplication
    /   <-- division
    %   < modulo operator - the remainder of the division

Loops

While loop

    int index = 1;
    while (index <= 5 )
    {
        Console.WriteLine(index);
        index++;
    }

Do While Loop

    int index = 1;
    do
    {
        Console.WriteLine(index);
        index++;
    } while (index <= 5 )

For Loop

    for(int i = 1; i <= 10; i++)
    {

    }

foreach Loop

Performance of for loop is better than performance of foreach loop.

    int[] nums = { 10, 20, 30, 40, 50 };
    foreach(int num in nums)
    {
        Console.WriteLine(num);
        // here num cannot be changed
    }

    static bool isAlphabetic(string str)
    {
        foreach(char c in str)
        { 
            if (! char.IsLetter(c))
            {
                return false;
            }
        }
        return true;
    }

Arrays

Initialization

    int[] numbers = new int[3];

    int[] numbers = new int[] {1, 2, 3, 4, 5};

    int[] numbers = new int[3] {1, 2, 3};

    int[] numbers = {1, 2, 3};

    int[,] array2D = { {1,2}, {3,4} };

Length

    int[] numbers = {1, 2, 3};
    numbers.Length;

Rank
```
    int dimensions = array2D.Rank;
```

Examples

    int[] luckyNumbers = { 4, 8, 15, 16, 23, 42};

    Console.WriteLine(luckyNumbers[0]); 

    luckyNumbers[1] = 900;

    for (int i = 0; i < luckyNumbers.Length; i++)
    {
        Console.WriteLine([i]);
    }

    string[] friends = new string[5]; // 5 is a size of the array

    friends[0] = "Jim";
    friends[1] = "John";

2D Arrays

    int[,] numberGrid = { 
        { 1, 2 }, // element at x position 0
        { 3, 4 },
        { 5, 6 }
    };

    Console.WriteLine(numberGrid[0, 0]); // row 0, column 0         is  1
    Console.WriteLine(numberGrid[1, 1]); // row 1, column 1         is  4

    int[,] myArray = new int[2, 3]; // 2 rows, 3 columns

```
    string[,] matrix;
```

    int[,] matrix = 
    {
        {1,2,3},
        {4,5,6},
        {7,8,9},
    }

    matrix.GetLength(0) // get number of rows
    matrix.GetLength(1) // get number of columns

    int[,] matrix =
    {
        {1,2,3},
        {4,5,6},
        {7,8,9},
    };

    foreach (int num in matrix)
    {
        Console.Write(num + " "); // output: 1 2 3 4 5 6 7 8 9
        // here num cannot be changed
    }

    for (int i = 0, j = matrix.GetLength(0) - 1; i < matrix.GetLength(0); i++, j--)
    {
        Console.Write(matrix[i, j] + " "); // output: 3 5 7
    }

    for (int i = 0; i < matrix.GetLength(0); i++)
    {
        for (int j = 0; j < matrix.GetLength(1); j++)
        {
            Console.Write(matrix[i, j] + " ");
        }
        Console.WriteLine();
    }    

    output:
    1 2 3
    4 5 6
    7 8 9

3D Arrays

    int[,,] numberGrid = { 
        { 1, 2, 7 }, // element at x position 0
        { 3, 4, 8 },
        { 5, 6, 9 }
    };

```
    int[,,] threeD;
```

Jagged Arrays - arrays within array

Declaration

    int[][] jaggedArray = new int[3][]; // three arrays within this jaggedArray    

    jaggedArray[0] = new int[5];
    jaggedArray[1] = new int[3];
    jaggedArray[2] = new int[2];

    int[][] jaggedArray = new int[3][]; // three arrays within this jaggedArray

    jaggedArray[0] = new int[] { 2, 3, 5, 7, 11 };
    jaggedArray[1] = new int[] { 1, 2, 3 };
    jaggedArray[2] = new int[] { 13, 21 };

    int[][] jaggedArray2 = new int[][]
    {
        new int[] { 2, 3, 5, 7, 11 },
        new int[] { 1, 2, 3 },
        new int[] { 13, 21 }
    };

Access Values

    Console.WriteLine("The value in the middle of the first entry is {0}", jaggedArray2[0][2]);

Example - print all values

    foreach (int[] item in jaggedArray2)
    {
        foreach (int num in item)
        {
            Console.Write(num + " ");
        }
        Console.WriteLine();
    }

    for (int i = 0; i < jaggedArray2.Length; i++)
    {
        for (int j = 0; j < jaggedArray2[i].Length; j++)
        {
            Console.Write(jaggedArray2[i][j] + " ");
        }
        Console.WriteLine();
    }

List, Lists

Initialization

    List<int> numbers = new List<int>();

    List<int> numbers = new List<int> {1, 2, 3};

    var numbers = new List<int>();

    var numbers = new List<int>{1, 5, 35, 100};

Print all elements of a list in C#

    Console.WriteLine(string.Join(", ", months));

More options

Adding value

    var numbers = new List<int>();
    numbers.Add(7);

Removing value

   
    numbers.Remove(7);    

    int index = 0;
    numbers.RemoveAt(index); // Remove an element at specific index

Getting a value

    var numbers = new List<int>();
    numbers.Add(7);
    
    int value = numbers[0];    // Will be 7

Clearing the whole list

    var numbers = new List<int>();
    numbers.Add(7);
    
    numbers.Clear();    // Deletes every element in our list

List and loops

    var numbers = new List<int>{1, 5, 35, 100};

    foreach(int element in numbers) {
        Console.Write(element);
    }

    for (int i = 0; i < numbers.Count; i++) {
        Console.Write(element);        
    }

Create a copy of the list

    public static List<string>GetFriends(List<string> list)
    {
        var buffer = new List<string>(list);
    }

ArrayLists

using System.Collections;

Initialization

    ArrayList myArrayList = new ArrayList();
OR
    ArrayList myArrayList = new ArrayList(100); // Will contain 100 objects

Usage

ArrayList myArrayList = new ArrayList();
myArrayList.Add(25);
myArrayList.Add("Hello");
myArrayList.Add(13.37);
myArrayList.Add(13);
myArrayList.Add(128);
myArrayList.Add(25.3);
myArrayList.Add(13);

myArrayList.Remove(13); // Delete the first element with specific value from the ArrayList

myArrayList.RemoveAt(0); // Remove the element at specific index at the ArrayList

Console.WriteLine($"Number of the elements are {myArrayList.Count}");  // number of elements

double sum = 0;
foreach (object obj in myArrayList)
{
    if (obj is int)
    {
        sum += Convert.ToDouble(obj);
    }
    else if(obj is double)
    {
        sum += (double)obj;
    }
    else if (obj is string)
    {
        Console.WriteLine(obj);
    }
}

Console.WriteLine($"Sum is {sum}");

HashTable

using System.Collections;

HashTable studentsTable = new HashTable();

studentsTable.Add(student1.Id, student1);

Retrieve individual item with known ID

Student storedStudent = (Student)studentsTable[student1.Id]  // retrieve a student object with ID student1.Id

Retrieve all values from HashTable - the better way

foreach(Student student in studentsTable.Values) 
{
    Console.WriteLine("{0}", student.Name)    
}

Retrieve all values from HashTable

foreach(DictionaryEntry student in studentsTable) 
{
    Student temp = (Student)student.Value;    
}

Insert into HashTable

HashTable table = new HashTable();

Student[] studentsArr = new Student[5];
studentsArr[0] = new Student(122, "Denis", "A");

foreach(Student student in studentsArr) 
{
    if (!table.ContainsKey(student.id))
    {
        table.Add(student.id, student);
    }
    else 
    {
        Console.writeLine("A student with the same ID already exist");
    }
}

Dictionary

    using System.Collections.Generic; // contains one data type only        
    Dictionary<TKey, TValue>

Initialization

   Dictionary<int, string> myDictionary = new Dictionary<int, string>();
OR
Dictionary<int, string> myDictionary = new Dictionary<int, string>() {
    { 1, "one" }
    { 2, "two" }
    { 3, "three" }}

Insert into a dictionary

Dictionary<string, Employee> employeeDictionary = new Dictionary<string, Employee>();
foreach(Employee emp in employees)
{
employeeDictionary.Add(emp.role, emp);
}

aDictionary.TryGetValue(key, out result)

if (employeeDictionary.TryGetValue(key, out result))
{
Console.WriteLine("Employee name", result.Name);
}
else
{
Console.WriteLine("The key does not exist");
}

aDictionary.ContainsKey(key)

string key = "CEO";
if (employeeDictionary.ContainsKey(key))
{
Employee emp = employeeDictionary[key];
}
else
{
Console.WriteLine("No employee found with {0} key", key); 
}

aDictionary.ElementAt(i)

using System.Linq;
for (int i = 0; i < employeeDictionary.Count; i++)
{
KeyValuePair<string, Employee> keyValuePair = employeeDictionary.ElementAt(i);

// Print the key
Console.WriteLine("Key: {0}, i is: {1}", keyValuePair.Key, i); // output: CEO    

// Storing the value in an employee object
Employee employee = keyValuePair.Value;

// Print a property of the employee
Console.WriteLine("{0}", employee.Name);

}

Update a value

string key = "HR";
if (employeeDictionary.ContainsKey(key))
{
   employeeDictionary[key] = new Employee("HR", "Erika", 26);
}

Remove a value

string key = "HR";
if (employeeDictionary.Remove(key)) // returns true if the item was removed
{
    Console.WriteLine("Employee with role {0} was removed.", key); 
}
else
{
    Console.WriteLine("No employee was found with this key");
}

Stack - LIFO - Last In First Out

Example of Use

Reversing order of data
Web browser back button
Undo/Redo buttons for performed operations

Stack Operations

Push(Object obj)
Pop()
Peek() - returns the object located at the top of the Stack

Stack Definition

using System.Collections.Generic; // contains one data type only        

Stack<int> stack = new Stack<int>();

Add a new item at the top
```
stack.Push(1);
```

See an element at the top of the stack without removing it.
```
int value = stack.Peek();
```

Remove a value from the top

if (stack.Count > 0)
{
    int value = stack.Pop();
}

Reversing an array

  int[] numbers = new int[] { 8, 2, 3, 4};

  // Defining a new stack of int
  Stack<int> myStack = new Stack<int>();  

  foreach(int num in numbers)
  {
     myStack.Push(num);
  }

  Console.Write("The numbers in reverse are: ");
  while(stack.Count > 0)
  {
     Console.Write("{0} ", stack.Pop());
  }

Queue - FIFO - First In First Out
- Queue at airport check-in
- Mouse Movements
- Enqueue(Object obj) - data is added at the rear
- Object Dequeue - data is removed from the front of the queue
- Peek() - returns the object located at the front of the Queue
- Definition
```
  using System.Collections.Generic; // contains one data type only 

  Queue<int> queue = new Queue<int>  
```
- Add items to the end of the queue
```
    queue.Enqueue(1);
```
- See a first item of the queue
```
int num = queue.Peek();
```
- Remove a first item of the queue
```
    if (queue.Count > 0)
        int num = queue.Dequeue();    
```

Collections - Generic and Non-Generic Collections

Non-Generic Collections

using System.Collections; // may contain different data types

Example See HashTable.

Example

using System.Collections;
...
int num1 = 5;
float num2 = 3.14f;
string name = "John";
ArrayList myArrayList = new ArrayList();
myArrayList.Add(num1);
myArrayList.Add(num2);
myArrayList.Add(name);

foreach(object element in myArrayList)
{
    Console.WriteLine(element);
}

Generic Collections

   using System.Collections.Generic; // contains one data type only

Examples
- Dictionary
- Stack
- Queue

Example

    using System.Collections.Generic;
    ...
    string animal1 = "Cat";
    string animal2 = "Dog";
    string animal3 = "Flamingo";
    List<string> myList = new List<string>();
    myList.Add(animal1);
    myList.Add(animal2);
    myList.Add(animal3);

    foreach (string animal in myList)
    {
        Console.WriteLine(animal);
    }

Comments

```
    // This is a single line comment
```

    /* 
    Multi 
    lines comment.
    */

Use /// to create XML documentation comments

    /// <summary>
    /// 
    /// </summary>
    /// <param name="args"></param>   
    static void Main(string[] args)
    {
        ...
    }

Exception Handling

try {

}
catch(Exception e) 
{
    Console.WriteLine(e.Message);
}
finally // will be executed always
{

}

try {

}
catch(Exception) 
{
    throw;
}

try {

}
catch 
{
    Console.WriteLine("Error");
}

try {
    Console.Write("Enter a number: ");
    double num1 = Convert.ToInt32(Console.ReadLine());

    Console.Write("Enter a number: ");
    double num2 = Convert.ToInt32(Console.ReadLine());


    Console.WriteLine(num1 / num2);
}
catch(DivideByZeroException e)
{
    Console.WriteLine(e.Message);
}
catch(FormatException e)
{
    Console.WriteLine(e.Message);
}
catch(Exception e)
{
    Console.WriteLine(e.Message);
}
finally // will be executed always
{
    
}

    throw new Exception("...");

Classes & Objects

Create a Class

Option # 1

                    At the right side of Visual Studio 
                    Open Solution Explorer
                    Under Solution 
                    Right Click on current project name
                    Press on Add > New Item 
                    Select a Class
                    Give a name to the class with a capital lettter.

                    As a result a new file with a Class was created.

Option # 2

                    At the main menu 
                    Project > Add a Class

Class with Constructor

    // Books.cs
    namespace Giraffe
    {
        class Book
        {
            public string title;
            public string author;
            public int pages;
        }

        // Default constructor
        public Book() {

        }

        // Parameterized constructor
        public Book(string aTitle, string aAuthor, int aPages)
        {
            title = aTitle;     // or this.title = aTitle;
            author = aAuthor;
            pages = aPages;
        }
    }

    // Program.cs
    namespace Giraffe
    {
        class Program
        {
            static void Main(string[] args)
            {
                Book book1 = new Book("Harry Potter", "JK Rowling", 400);

                book1.title = "The hobbit";  // Update value
                Console.WriteLine(book2.title);

                Book book2 = new Book();

                Console.ReadLine();
            }
        }
    }

Simple Class Example

                        // Books.cs
                        namespace Giraffe
                        {
                            class Book
                            {
                                public string title;
                                public string author;
                                public int pages;
                            }
                        }

                        // Program.cs
                        namespace Giraffe
                        {
                            class Program
                            {
                                static void Main(string[] args)
                                {
                                    Book book1 = new Book();
                                    book1.title = "Harry Potter";
                                    book1.author = "JK Rowling";
                                    book1.pages = 400;
                    
                                    Console.WriteLine(book1.title);
                    
                                    Console.ReadLine();
                                }
                            }
                        }

Destructor - finalizer

Can be only one Destructor in the class. Slows performance.

    ~Book()
    {
        // Cleanup Statements when object of the class is runs out of scop
        Console.WriteLine("Deconstruction of the object");                    
        Debug.WriteLine("Deconstruction of the object!");
    }

Access Modifiers
- Article
- Documentation

Object Methods

        // Student.cs
        namespace Giraffe
        {
            class Student 
            {
                private string name;
                private string major;
                private double gpa;

                public Student(string aName, string aMajor, double aGpa)
                {
                    name = aName;
                    major = aMajor;
                    gpa = aGpa;
                }

                public bool HasHonors()
                {
                    if (gpa >= 3.5) 
                    {
                        return true;
                    }
                    return false;
                }
            }
        }

        // Program.cs
        namespace Giraffe
        {
            class Program
            {
                static void Main(string[] args)
                {
                    Student student1 = new Student("Jim", "Business", 2.8);

                    Console.WriteLine(student1.HasHonors()); // False

                    Console.ReadLine();            
                }
            }
        }

Getter and Setters

        // Movie.cs
        namespace Giraffe
        {
            class Movie 
            {
                private string title;
                private string director;
                private string rating;

                public Movie(string aTitle, string aDirector, string aRating)
                {
                    title = aTitle;
                    director = aDirector;
                    Rating = aRating;  // rating will be set through the Rating setter.
                }

                public string Rating
                {
                    get { return rating; }
                    set { rating = value; }

                    OR
                    
                    set { 
                        if (value  == "G" || value == "PG")          // value is a value that was passed
                        {
                            rating = value;
                        }
                        else 
                        {
                            rating = "NR";
                        }              
                    }
                }
            }
        }

Default getter and setter

        public string Rating { get; set; } // property   // private string rating; is not required to be defined

        // Constructor will be:
        public Movie(aRating)
        {
            Rating = aRating;
        }

    Same as
        private string rating; // member value
        public string Rating
        {
            get { return this.rating; }
            set { this.rating = value; }
        }

        // Program.cs
        namespace Giraffe
        {
            class Program
            {
                static void Main(string[] args)
                {
                    Movie shrek = new Movie("Shrek", ""Adam Adamson, "PG");
                    
                    Console.WriteLine(shrek.Rating);  <--- using the getter

                    shrek.Rating = "Cat";       <--- using the setter
                    Console.ReadLine();
                }
            }
        }

Static Class Attributes

Are shared by all objects of the class.

            class Song 
            {        
                public static int songCount = 0;  
                public static title;   

                public Song(string aTitle)
                {
                    title = aTitle;
                    songCount++;
                }
            }

            class Program
            {
                Song holiday = new Song("Holiday");
                Console.WriteLine(Song.songCount);
            }

Static Methods

Methods that belongs to a class. we don't need to create an instance of the class in order to use it.

            class UsefulTools
            {
                public static void SayHi(string name)        
                {
                    Console.writeLine("Hello " +  name);
                }
            }

            class Program
            {
                UsefulTools.SayHi("Mike");
            }

Static Class

            static class UsefulTools  // We cannot create an instance of the class
            {
                public static void SayHi(string name)        
                {
                    Console.writeLine("Hello " +  name);
                }
            }

Inheritance

Examples

Example #1

namespace InheritanceProj
{
    // Parent class
    class ElectricDevice
    {
        public bool IsOn {get; set; }

        public string Brand { get; set; }

        public void SwitchOff()
        {
            IsOn = false;
        }

        public void SwitchOn()
        {
            IsOn = true;
        }

        public ElectricDevice(bool isOn, string brand)
        {
            IsOn = isOn;
            Brand = brand;
        }
    }
}

namespace InheritanceProj
{
    // Child class
    class Radio : ElectricDevice
    {
        public Radio(bool isOn, string brand) : base(isOn, brand)
        {

        }

        public void ListenRadio()
        {
            if (IsOn)
            {
                Console.WriteLine("Listening to the Radio");
            }
            else
            {
                Console.WriteLine("Radio is switched off, switch it on first.");
            }
        }

        public void SwitchOn()
        {
            IsOn = true;
        }

        public void SwitchOff()
        {
            IsOn = false;
        }
    }
}

namespace InheritanceProj
{
    class Program
    {
        static void Main(string[] args)
        {
            Radio radio = new Radio(false, "LG");
            // radio.SwitchOn();

            radio.ListenRadio();

            TV tv = new TV(true, "Sony");
            
            tv.WhatchTV();
        }
    }
}

Example #2

// Chef.cs
namespace Giraffe
{
    class Chef      // A super class
    {    
        public void MakeChicken()
        {
            Console.WriteLine("The Chef makes chicken");
        }

        public void MakeSalad()
        {
            Console.WriteLine("The Chef makes salad");
        }

        public virtual void MakeSpecialDish()        // virtual - sub classes may override this method
        {
            Console.WriteLine("The Chef makes bbq ribs");
        }
    }
}

// ItalianChef.cs
namespace Giraffe
{
    class ItalianChef : Chef    // inherits from Chef class - a sub class
    {
        public void MakePasta()
        {
            Console.WriteLine("The Chef makes pasta");
        }

        public override void MakeSpecialDish()      // override - overrides a virtual method
        {
            Console.WriteLine("The Chef makes chicken parm");
        }        
    }
}

// Program.cs
namespace Giraffe
{
    class Program
    {
        static void Main(string[] args)
        {
            Chef chef = new Chef();
            chef.MakeChicken();
            chef.MakeSpecialDish();

            ItalianChef italianChef = new ItalianChef();
            italianChef.MakeChicken();            
            italianChef.MakeSpecialDish();

            Console.ReadLine();
        }
    }
}

Console Class and some of its Methods

    Console.ForegroundColor = ConsoleColor.Green; // Change color of the text
    Console.BackgroundColor = ConsoleColor.Gray;
    Console.Clear(); // Colors the whole console terminal in the background color

    Console.WriteLine("num1: " + num1); // Prints the content and jumps to a new line.

    Console.WriteLine("The value is {0}", num1); // Prints the content and jumps to a new line.
    
    Console.Write("Hello");   // Prints the text in the same line 
    
    string input = Console.ReadLine(); // Takes a string or integer input and returns it as the Output value.
    
    int asciiValue = Console.Read();     // Takes a single input of type string and it returns the ASCII value of that input.
    
    Console.ReadKey();  // Takes a single input of type string and it returns the Key Info.

Examples:

    string name;
    Console.WriteLine("Please enter your name and press enter");
    name = Console.ReadLine();

    Console.WriteLine($"Hi {name}");

Concatenation of two input strings

Solution # 1

    Console.WriteLine("Please Enter Your First name and press Enter");
    string firstName = Console.ReadLine();
    Console.WriteLine("Please Enter Your last name and press Enter");
    string lastName = Console.ReadLine();

    string fullName = string.Concat(firstName, " ", lastName);
    
    Console.WriteLine($"Welcome {fullName}");

Solution # 2

    Console.WriteLine("Please Enter Your First name and press Enter");
    string firstName = Console.ReadLine();
    Console.WriteLine("Please Enter Your last name and press Enter");
    string lastName = Console.ReadLine();

    string fullName = $"{firstName} {lastName}";
    Console.WriteLine($"Welcome {fullName}");

Find index of char in the input string

Solution # 1

    Console.WriteLine("Please enter a string");
    string inputStr = Console.ReadLine();
    Console.WriteLine("Enter the character to search:");
    char ch = Console.ReadLine()[0];

    int indx = inputStr.IndexOf(ch);

    Console.WriteLine($"\n Index of char is {indx}");

Solution # 2

    Console.WriteLine("Please enter a string");
    string inputStr = Console.ReadLine();
    Console.WriteLine("Enter the character to search:");
    ConsoleKeyInfo ch = Console.ReadKey();
    Console.WriteLine(ch.KeyChar);

    int indx = inputStr.IndexOf(ch.KeyChar);

    Console.WriteLine($"\n Index of the char is {indx}");

Threads - run things in parallel on multi core processor

More info

New Thread Creation

    using System.Threading;
    ...

    new Thread(() => 
    {
        Console.WriteLine($"Thread Id: {Thread.CurrentThread.ManagedThreadId} has started");
        Thread.Sleep(1000);
        Console.WriteLine($"Thread Id: {Thread.CurrentThread.ManagedThreadId} has ended");     

    }).Start();

New Thread Creation at the Background

    new Thread(() =>
    {
        Thread.Sleep(1000);
        Console.WriteLine("Thread 4");
    })
    { IsBackground = true }.Start();

Examples

Delay the main thread for 1 second

using System;
using System.Threading;

namespace ThreadingE
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello 1");
            Thread.Sleep(1000); // stopping the main thread for 1 seconds
            Console.WriteLine("Hello 2");
            Console.WriteLine("Hello 3");
            Console.WriteLine("Hello 4");

            Console.ReadKey();
        }
    }
}

Multi threading example

    new Thread(() =>
    {
        Thread.Sleep(1000);
        Console.WriteLine("Thread 1");
    }).Start();

    new Thread(() =>
    {
        Thread.Sleep(1000);
        Console.WriteLine("Thread 2");
    }).Start();

    new Thread(() =>
    {
        Thread.Sleep(1000);
        Console.WriteLine("Thread 3");
    }).Start();

Task completion

    using System.Threading;
    using System.Threading.Tasks;
    ...

    var taskCompletionSource = new TaskCompletionSource<bool>();

    var thread = new Thread(() =>
    {
        Console.WriteLine($"Thread Id: {Thread.CurrentThread.ManagedThreadId} has started");
        Thread.Sleep(1000);
        taskCompletionSource.TrySetResult(true);
        Console.WriteLine($"Thread Id: {Thread.CurrentThread.ManagedThreadId} has ended");
    });

    // Console.WriteLine($"Thread Id: {thread.ManagedThreadId}");
    thread.Start();
    var result = taskCompletionSource.Task.Result;
    Console.WriteLine($"Task was done with result {result}");

Thread Pool

All threads in the Thread Pool run at the background. Thread Pool re-uses the threads. Thread Pool does not clean the data at the local storage.

Enumerable.Range(0, 1000).ToList().ForEach(f =>   
{
    ThreadPool.QueueUserWorkItem((obj) =>
    {
        Console.WriteLine($"Thread Id: {Thread.CurrentThread.ManagedThreadId} has started");
        Thread.Sleep(1000);
        Console.WriteLine($"Thread Id: {Thread.CurrentThread.ManagedThreadId} has ended");
    });
});

Join - blocking the calling thread

        namespace ThreadingE
        {
            class Program
            {
                static void Main(string[] args)
                {
                    Console.WriteLine("Main Thread started");

                    Thread thread1 = new Thread(Thread1Function);
                    Thread thread2 = new Thread(Thread2Function);
                    thread1.Start();
                    thread2.Start();


                    thread1.Join();  // blocking the calling (here the main) thread
                    Console.WriteLine("Thread1Function done");
                    thread2.Join();
                    Console.WriteLine("Thread2Function done");

                    Console.WriteLine("Main Thread ended");
                    
                    
                    Console.ReadKey();
                }

                static void Thread1Function()
                {
                    Console.WriteLine("Thread1Function started");
                    Thread.Sleep(3000);
                }

                static void Thread2Function()
                {
                    Console.WriteLine("Thread2Function started");
                }
            }
        }

        namespace ThreadingE
        {
            class Program
            {
                static void Main(string[] args)
                {
                    Console.WriteLine("Main Thread started");

                    Thread thread1 = new Thread(Thread1Function);
                    Thread thread2 = new Thread(Thread2Function);
                    thread1.Start();
                    thread2.Start();


                    if (thread1.Join(1000)) // timeout of 1 seconds
                    {
                        Console.WriteLine("Thread1Function done within 1 seconds");
                    }
                    else
                    {
                        Console.WriteLine("Thread1Function wasn't done within 1 seconds");
                    }

                    thread2.Join();
                    Console.WriteLine("Thread2Function done");

                    Console.WriteLine("Main Thread ended");
                    
                    
                    Console.ReadKey();
                }

                static void Thread1Function()
                {
                    Console.WriteLine("Thread1Function started");
                    Thread.Sleep(3000);
                    Console.WriteLine("Thread1Function coming back to main");
                }

                static void Thread2Function()
                {
                    Console.WriteLine("Thread2Function started");
                }
            }
        }

isAlive

    if (thread1.IsAlive)
    {
        Console.WriteLine("Thread1 is still doing staff");
    }
    else
    {
        Console.WriteLine("Thread1 completed");
    }

namespace ThreadingE
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Main Thread started");

            Thread thread1 = new Thread(Thread1Function);
            Thread thread2 = new Thread(Thread2Function);
            thread1.Start();
            thread2.Start();


            if (thread1.Join(1000)) // timeout of 1 seconds
            {
                Console.WriteLine("Thread1Function done within 1 seconds");
            }
            else
            {
                Console.WriteLine("Thread1Function wasn't done within 1 seconds");
            }

            thread2.Join();
            Console.WriteLine("Thread2Function done");

            for (int i = 0; i < 10; i++)
            {
                if (thread1.IsAlive)
                {
                    Console.WriteLine("Thread1 is still doing staff");
                    Thread.Sleep(300);
                }
                else
                {
                    Console.WriteLine("Thread1 completed");
                }

            }

            Console.WriteLine("Main Thread ended");
            
            
            Console.ReadKey();
        }

        static void Thread1Function()
        {
            Console.WriteLine("Thread1Function started");
            Thread.Sleep(3000);
            Console.WriteLine("Thread1Function coming back to main");
        }

        static void Thread2Function()
        {
            Console.WriteLine("Thread2Function started");
        }
    }
}

Debugging Threads

Debug > Windows > Threads (same as Ctrl Alt H)

Useful Links

50+ Interview Questions For Your CSharp Interview

How to check a palindrome number in C# Programming

Armstrong Number and how to check it with C#

What is the Fibonacci Sequence and how to use it in C#

What is a prime number, and how to generate prime numbers using C# programming

Tools

Microsoft Visual Studio
See here

Resources

Great video about C#.

Course on Udemy: Complete C# Masterclass

Back

C# summary

Numbers

Whole Numbers

int - whole numbers from -2,147,483,648 to 2,147,483,647

More Numbers

float

double

decimal

Calculation

Constants

Casting

Implicit Conversion

Explicit Conversion

Type Conversion

String Interpolation - starts with $

Verbatim String - starts with @

String Formatting

Parsing a string to integer

Parsing a string to float

params

If statement

Ternary Operator

Switch statement

Conditional (logical) operators

Comparison operators

Unary operators

!

-

Increment operator

Decrement operator

Math operators

Initialization

Length

Rank

Examples

Jagged Arrays - arrays within array

Declaration

Access Values

Example - print all values

Initialization

Print all elements of a list in C#

Adding value

Removing value

Getting a value

Clearing the whole list

List and loops

Create a copy of the list

Retrieve individual item with known ID

Retrieve all values from HashTable - the better way

Retrieve all values from HashTable

Insert into HashTable

Initialization

Insert into a dictionary

aDictionary.TryGetValue(key, out result)

aDictionary.ContainsKey(key)

aDictionary.ElementAt(i)

Update a value

Remove a value

Stack - LIFO - Last In First Out

Example of Use

Stack Operations

Push(Object obj)

Pop()

Peek() - returns the object located at the top of the Stack

Stack Definition

Add a new item at the top

See an element at the top of the stack without removing it.

Remove a value from the top

Reversing an array

Queue - FIFO - First In First Out

Example of Use:

Queue Operations

Enqueue(Object obj) - data is added at the rear

Object Dequeue - data is removed from the front of the queue

Peek() - returns the object located at the front of the Queue

Definition

Add items to the end of the queue

See a first item of the queue

Remove a first item of the queue

Non-Generic Collections

`params`