C# Tutorials
C# Introduction
C# Syntax
C# Comments
C# Variables
C# DataTypes
C# Operators
C# Strings
C# Math
C# Booleans
C# If..else
C# Switch
C# WhileLoop
C# For Loop
C# Break
C# Arrays
C# Methods
C# Methods
C# Method Parameters
C# Method Overloading
C# Classes
C# OOP
C# Classes/Objects
C# Class Members
C# Access Modifiers
C# Properties
C# Inheritance
C# Polymorphism
C# Abstraction
C# Interface
C# Enums
C# Files
C# Exceptions
C# Examples
C# Compiler
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C# Variables
Variables are data storage containers.
In C #, there are different types of variables (defined by different keywords), for example:
- int-keeps numbers (whole numbers), without decimals, such as 123 or -123
- double-keeps floating points, with decimals, such as 19.99 or 19.99
- char-keeps single characters, such as 'a' or 'B'. Char values are surrounded by single quotes
- string-retains text, such as "Hello World". Character unit values are surrounded by two quotes
- bool-keeps values in two forms: true or false
Declaring (Creating) Variables
To create a variable, you must specify a type and assign a value:
Syntax
"type variableName"
=
"value"
;
Where type is type C# (like int or string), and variableName is a variable name (such as x or name).
The equal symbol is used for variable values
To create an alternative that should keep the text, see the following example:
Example
Make a variable called name of type string and assign it the value "John":
string
"name"
=
"John"
;
"Console"
.
WriteLine
(
"name"
)
;
To create an alternative that should keep the number, see the following example:
Example
Make a variable called myNum of type int and assign it the value 15:
int
"myNum"
=
15
;
"Console"
.
WriteLine
(
"myNum"
)
;
You can also declare the variable without giving value, and provide value later:
Example
int
"myNum"
;
"myNum"
=
15
;
"Console"
.
WriteLine
(
"myNum"
)
;
Note that if you assign a new value to an existing variant, it will delete the previous value:
Example
Change myNum value to 20:
int
"myNum"
=
15;
"myNum"
=
20
; // myNum is now 20
"Console"
.
WriteLine
(
"myNum"
)
;
Constants
However, you can add a keyword const if you do not want others (or you yourself) to write over existing values (this will declare the variable as "continuous", meaning that it cannot be changed and read only):
Example
const
int
"myNum"
=
15
;
"myNum"
=
20
; // error
Other Types
Demonstration of how to advertise variable in other genres:
Example
int
"myNum"
=
5
;
double
"myDoubleNum"
=
5.99
"D"
;
char
"myLetter"
=
'D'
;
bool
"myBool"
=
true
;
string
"myText"
=
"Hello"
;
Display Variables
The WriteLine() method is often used to display variable values in the console window.
To combine both text and variable, use the + character:
Example
string
"name"
=
"John"
;
"Console"
.
WriteLine
(
"Hello " +
"name"
)
;
You can also use the character + to add variables to other variables:
Example
string
"firstName"
=
"John "
;
string
"lastName"
=
"Doe"
;
string
"fullName"
= "firstName"
+ "lastName"
;
"Console"
.
WriteLine
(
"fullName"
)
;
In numerical values, the character + acts as a mathematical operator (note that we use int (integer) variables here):
Example
int
"x"
=
5
;
int
"y"
=
6
;
"Console"
.
WriteLine
(
"x"
+
"y"
)
; // Print the value of x + y
In the example above, you can expect:
- x stores the value 5
- y stores the value 6
- Then we use the WriteLine() method to display the x + y value, which is 11
Declare Many Variables
To declare more than one variable of the same type, use a comma-separated list:
Example
int
"x"
=
5
,
"y"
=
6
,
"z"
=
50
;
Console
.
WriteLine
(
"x"
+
"y"
+
"z"
)
;
C# Identifiers
All C# variables must be identified by different names.
These unique names are called identifiers.
Identifiers can be short words (such as x and y) or multiple descriptive words (age, total, volume).
Note: It is recommended to use descriptive words to create understandable and sustainable code:
Example
// Good
int
"minutesPerHour"
=
60
;
"// OK, but not so easy to understand what" m
"actually is"
int
"m"
=
60
;
The general rules for naming variables are:
- Names may contain letters, digits, and the underscore (_) character
- Names should start with a letter
- Names should start with a lower case letter and cannot contain white space
- Names are case sensitive ("myVar" and "myvar" are different variables)
- Reserved words (like C# keywords, such as int or double) cannot be used as names