Introduction to C#

• C# is pronounced "C-Sharp".
• Microsoft created C# as an object-oriented programming language.
• C# runs on the .NET Framework, and has roots in the C family.
• C++ and Java are languages related to C#.
• C# version was released in 2002, and C# 8 was released in September 2019.

C# Applications

• C# is utilized in:
• Mobile applications
• Desktop applications
• Web applications
• Web services
• Web sites
• Games
• Augmented & Virtual Reality

Reasons to Use C#

• C# is a popular programming language
• C# is easy to learn and simple to use
• Support from a huge community
• Programs have object-oriented structure that allows code reuse, lowering development costs
• Programmers can easily switch to C# or vice versa, because C# is close to C, C++, and Java

C# IDE

• The easiest way to get started with C# is to use an IDE.
• IDE stands for Integrated Development Environment, and is used to edit and compile code.
• Visual Studio Community is used to edit and compile code
• It is free to download.
• Applications written in C# use the .NET Framework, in Visual Studio as program, framework, and language, created by Microsoft

C# Syntax

• using System statements are used to use classes from the corresponding System namespace.
• Whitespace is ignored, but multiple lines could make code more readable.
• Namespaces organize code into containers for classes and other namespaces.
• Curly braces denote the beginning and end of a block of code.
• Data and methods are stored in classes that bring functionality to a program, and must be inside a class.
• Console is a class of the System namespace and makes use of WriteLine() to output/print text.

C# Syntax

• Use a semicolon to end every C# statement.
• C# is case-sensitive: "MyClass" differs from "myclass".
• C# filenames can differ from the class name but are saved it using a proper name and add ".cs"

WriteLine/Write Methods

• WriteLine() is the most common method to output something in C#, however, Write() can also be used.
• WriteLine() prints the output on a new line each time, Write() prints on the same line.

C# Comments

• Comments explain C# code, make it readable, and prevent execution during alternative code testing.

Single Line Comments

• Single-line comments start with two forward slashes //.
• Text between // and the end of the line is ignored by C#.

Multi-Line Comments

• Multi-line comments start with /* and end with */.
• All text between /* and */ is not executed in C#.

C# Data Types

• bool: Boolean value, which can be true or false, with a false default.
• byte: 8-bit unsigned integer from 0 to 255, , with a default of 0.
• char: 16-bit Unicode character from U +0000 to U +ffff, with a default of '\0'.
• decimal: 128-bit precise decimal value with 28-29 significant digits from (-7.9 x 1028 to 7.9 x 1028) / 100 to 28, with a default of 0.0M.
• double: 64-bit double-precision floating point type from (+/-)5.0 x 10-324 to (+/-)1.7 x 10308, with a default of 0.0D.
• float: 32-bit single-precision floating point type from -3.4 x 1038 to + 3.4 x 1038, with default of 0.0F.
• int: 32-bit signed integer type from -2,147,483,648 to 2,147,483,647, with a default of 0.
• long: 64-bit signed integer from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807, with a default of 0L.
• sbyte: 8-bit signed integer type from -128 to 127, with a default of 0.
• short: 16-bit signed integer type from -32,768 to 32,767, with default of 0.
• uint: 32-bit unsigned integer type from 0 to 4,294,967,295, with a default of 0
• ulong: 64-bit unsigned integer type from 0 to 18,446,744,073,709,551,615, with a default of 0.
• ushort: 16-bit unsigned integer type from 0 to 65,535, with a default of 0.

Type Casting

• Type casting occurs when a value of one data type is assigned to another type.
• There are implicit and explicit casting

Implicit Casting

• Implicit casting converts a smaller type to a larger type automatically.
• char -> int -> long -> float -> double

Explicit Casting

• Explicit casting converts a larger type to a smaller size type.
• double -> float -> long -> int -> char
• Explicit casting must be manually done by placing the type in parentheses in front of the value.

Type Conversion Methods

• Data types may be converted explicitly by built-in methods.
• Methods of Convert:
• Convert.ToBoolean, Convert.ToDouble, Convert.ToString
• Convert.ToInt32 (int), Convert.ToInt64 (long)

User Input

• Console.WriteLine() outputs to the screen,.
• Console.ReadLine() gets user input.
• Console.ReadLine() method returns a string, which you can't extract information from another data type like int.
• The Type Casting Methods allow you to convert any type by using Convert.To methods.

C# Conditions and if Statements

• Common logical conditions:
• Less than: a < b
• Less than or equal to: a <= b
• Greater than: a > b
• Greater than or equal to: a >= b
• Equal to: a == b
• Not Equal to: a != b
• Conditions can perform different actions for different decisions.

C# if statements

• Use if to specify a block of code to be executed, if a specified condition is true.
• Use else to specify a block of code to be executed, if the same condition is false.
• Use else if to specify a new condition to test, if the first condition is false.
• Use switch to specify many alternative blocks of code to be executed.

if statement

• The if statement specifies a C# code block to be executed if a condition is True.
• if (condition) { // block of code to be executed if the condition is True }

else statement

• The else statement specifies a block of code to be executed if the condition is False.
• if (condition) { // block of code to be executed if the condition is True } else { // block of code to be executed if the condition is False }

else if Statement

• The else if statement specifies a new condition if the first condition is False.
• if (condition1) { // block of code to be executed if condition1 is True } else if (condition2) { // block of code to be executed if the condition1 is false and condition2 is True } else { // block of code to be executed if the condition1 is false and condition2 is False }

switch Statement

• The switch statement selects one out of many code blocks to be executed.
• The switch expression is evaluated once.
• The value of the expression is compared with each case.
• The block of code is executed following a successful match.

break Keyword

• The break keyword breaks out of the switch block.
• It stops any future code or cases inside the block from executing/testing.
• There is no need for more testing, once a match is found, and the job is done.
• The break can save execution time because it "ignores" the execution of the rest of the code in the switch block.

default Keyword

• The default keyword is optional.
• It specifies code to run if there is no case match

Iteration Structures (Loops)

• Loops in execute a block of code repeatedly until a specified condition is met
• Loops reduce code redundancy and automate repetitive tasks
• Types include the for, while, and do while loops

for Loop

• Used when the number of iterations is known
• Consists of initialization, condition, and iteration statements
• The initialization sets the starting value of the loop variable
• The condition defines when to execute the loop
• The iteration updates the loop variable after each repetition

while Loop

• Repeats a block of code as long as a condition remains true
• The condition is checked before each execution of the loop

·do while· Loop

• Guarantees that the block of code will be executed at least once
• Even if the condition is initially false

Order of Precedence

• Refers to the order in which operators are evaluated in an expression
• Operator precedence determines which operations are completed first in complex expressions with multiple operators

Operator Precedence (High to Low)

• Parentheses ()
• Unary operators such as increment ++, decrement --, plus + and minus -
• Multiplication *, division /, and modulus %
• Addition + and subtraction -
• Relational operators such as <, >, <=, and >=
• Equality operators such as == and !=
• Logical AND &&
• Logical OR ||
• Assignment =