Introduction to C sharp

Introduction to C sharp

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WHAT IS C#?

You pronounce C# as "C-Sharp."

It is a Microsoft-developed object-oriented programming language that utilizes the.NET Framework.

C# is related to other widely used languages like C++ and Java and has origins in the C family.

In 2002, the initial version was made available. In November 2022, C# 11, the most recent version, was published.

Uses for C# include:

Mobile programs Using desktop programs Web-based programs Online services websites, video games, and database programmes.

Why Use C#?

1.] It is one of the most popular programming languages in the world.

2.] It is easy to learn and simple to use.

3.] It has huge community support.

4.] C# is an object-oriented language that gives a clear structure to programs and allows code to be reused, lowering development costs.

5.] As C# is close to C, C++ and Java, it makes it easy for programmers to switch to C# or vice versa.

C# SYNTAX

We created a C# file called Program.cs, and we used the following code to print "Hello World" to the screen:

using System;

namespace HelloWorld
{
  class Program
  {
    static void Main(string[] args)
    {
      Console.WriteLine("Hello World!");    
    }
  }
}

line 1.] The use of the System namespace allows us to use classes.

Line 2.] It is left empty. White space is ignored in C#. The code is better understood when there are more lines, though.

Line 3.] A namespace serves as a container for classes and other namespaces and is used to structure your code.

Line 4.] A block of code has a beginning and an end indicated by curly brackets.

Line 5.] A class is a container for data and operations that gives your application functionality. Every line of C# code that executes must be contained within a class. We gave the class in our example the name Program.

Line 6.] Another thing that always appears in a C# program, is the Main method. Any code inside its curly brackets {} will be executed. You don't have to understand the keywords before and after Main. You will get to know them bit by bit while reading this tutorial.

Line 7.] Console is a class of the System namespace, which has a WriteLine() methods that are used to output/print text. In our example, it will output "Hello World!".

Note: Every C# statement ends with a semicolon ;.

Note: C# is case-sensitive: "MyClass" and "myclass" has a different meaning.

Note: Unlike Java, the name of the C# file does not have to match the class name, but they often do (for better organization). When saving the file, save it using a proper name and add ".cs" to the end of the filename. To run the example above on your computer, make sure that C# is properly installed.

C# Output

To output values or print text in C#, you can use the WriteLine() method:

Console.WriteLine("Hello World!");

You can add as many WriteLine() methods as you want. Note that it will add a new line for each method:

Console.WriteLine("Hello World!");
Console.WriteLine("I am Learning C#");
Console.WriteLine("It is awesome!");

You can also output numbers, and perform mathematical calculations:

The Write Method

There is also a Write() method, which is similar to WriteLine().

The only difference is that it does not insert a new line at the end of the output:

Console.Write("Hello World! ");
Console.Write("I will print on the same line.");

C# Comments

Comments can be used to explain C# code, and to make it more readable. It can also be used to prevent execution when testing alternative code.

Single-line Comments

Single-line comments start with two forward slashes (//).

Any text between // and the end of the line is ignored by C# (will not be executed).

This example uses a single-line comment before a line of code:

// This is a comment
Console.WriteLine("Hello World!");

This example uses a single-line comment at the end of a line of code:

Console.WriteLine("Hello World!");  // This is a comment

C# Multi-line Comments

Multi-line comments start with /* and ends with */.

Any text between /* and */ will be ignored by C#.

This example uses a multi-line comment (a comment block) to explain the code:

C# Variables

Variables are containers for storing data values.

In C#, there are different types of variables (defined with different keywords), for example:

  • int - stores integers (whole numbers), without decimals, such as 123 or -123

  • double - stores floating point numbers, with decimals, such as 19.99 or -19.99

  • char - stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes

  • string - stores text, such as "Hello World". String values are surrounded by double quotes

  • bool - stores values with two states: true or false

Declaring (Creating) Variables

To create a variable, you must specify the type and assign it a value:

type variableName = value;

Where type is a C# type (such as int or string), and variableName is the name of the variable (such as x or name). The equal sign is used to assign values to the variable.

To create a variable that should store text, look at the following example:

string name = "Iliyan";
Console.WriteLine(name);

To create a variable that should store a number, look at the following example:

int myNum = 33;
Console.WriteLine(myNum);

You can also declare a variable without assigning the value, and assign the value later:

int myNum;
myNum = 33;
Console.WriteLine(myNum);

Note that if you assign a new value to an existing variable, it will overwrite the previous value:

int myNum = 33;
myNum = 43; // myNum is now 43
Console.WriteLine(myNum);

Other Types

A demonstration of how to declare variables of other types:

int myNum = 33;
double myDoubleNum = 5.99D;
char myLetter = 'I';
bool myBool = true;
string myText = "Hello";

C# Data Types

As explained in the variables chapter, a variable in C# must be a specified data type:

int myNum = 5;               // Integer (whole number)
double myDoubleNum = 5.99D;  // Floating point number
char myLetter = 'D';         // Character
bool myBool = true;          // Boolean
string myText = "Hello";     // String

A data type specifies the size and type of variable values.

It is important to use the correct data type for the corresponding variable; to avoid errors, to save time and memory, but it will also make your code more maintainable and readable.

Integer Types

Int

The int data type can store whole numbers from -2147483648 to 2147483647. In general, and in our tutorial, the int data type is the preferred data type when we create variables with a numeric value.

int myNum = 100000;
Console.WriteLine(myNum);

Long

The long data type can store whole numbers from -9223372036854775808 to 9223372036854775807. This is used when int is not large enough to store the value. Note that you should end the value with an "L":

long myNum = 33333330000;
Console.WriteLine(myNum);

Try it Yourself »

Floating Point Types

You should use a floating point type whenever you need a number with a decimal, such as 9.99 or 3.14515.

The float and double data types can store fractional numbers. Note that you should end the value with an "F" for floats and "D" for doubles:

float myNum = 5.75F;
Console.WriteLine(myNum);

Double Example

double myNum = 19.99D;
Console.WriteLine(myNum);

Booleans

A boolean data type is declared with the bool keyword and can only take the values true or false:

bool isCSharpFun = true;
bool isFishTasty = false;
Console.WriteLine(isCSharpFun);   // Outputs True
Console.WriteLine(isFishTasty);   // Outputs False

Characters

The char data type is used to store a single character. The character must be surrounded by single quotes, like 'A' or 'c':

char myGrade = 'B';
Console.WriteLine(myGrade);

Strings

The string data type is used to store a sequence of characters (text). String values must be surrounded by double quotes:

string greeting = "Hello World";
Console.WriteLine(greeting);

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