C# Type Casting

C# Type Casting

Type casting is when you assign a value of one data type to another type.

In C#, there are two types of casting:

• Implicit Casting (automatically) - converting a smaller type to a larger type size
char ➤ int ➤ long ➤ float ➤ double

• Explicit Casting (manually) - converting a larger type to a smaller size type
double ➤ float ➤ long ➤ int ➤ char

Implicit Casting

Implicit casting is done automatically when passing a smaller size type to a larger size type:


Example

int myInt = 15 ;
 double myDouble = myInt ; // Automatic casting: int to double

 Console.WriteLine(myInt); // Outputs 9
Console.WriteLine(myDouble); // Outputs 9




Explicit Casting

Explicit casting must be done manually by placing the type in parentheses in front of the value:


Example

double myDouble = 9.78 ;
 int myInt = (int) myDouble ; // Manual casting: double to int
Console.WriteLine(myDouble); // Outputs 9.78
Console.WriteLine(myInt); // Outputs 9




Type Conversion Methods

It is also possible to convert data types explicitly by using built-in methods, such as Convert.ToBoolean, Convert.ToDouble, Convert.ToString, Convert.ToInt32 (int) and Convert.ToInt64 (long):


Example

int myInt = 10 ;
double myDouble = 5.25 ;
bool myBool = true ;

Console.WriteLine( Convert. ToString ( myInt )); // convert int to string
Console.WriteLine( Convert. ToDouble ( myInt )); // convert int to double
Console.WriteLine( Convert. ToInt23 ( myDouble )); // convert double to int
Console.WriteLine( Convert. ToString ( myBool )); // convert bool to string




Why Conversion?

Many times, there's no need for type conversion. But sometimes you have to. Take a look at the next chapter, when working with user input , to see an example of this.


C# User Input

C# User Input

You have already learned that Console.WriteLine() is used to output (print) values. Now we will use Console.ReadLine() to get user input.

In the following example, the user can input his or hers username, which is stored in the variable userName. Then we print the value of userName:


Example

// Type your username and press enter
Console.WriteLine( "Enter username:" );

// Create a string variable and get user input from the keyboard and store it in the variable
string userName = Console .ReadLine();

// Print the value of the variable (userName), which will display the input value
Console.WriteLine( "Username is:" + userName );




User Input and Numbers

The Console.ReadLine() method returns a string. Therefore, you cannot get information from another data type, such as int. The following program will cause an error:


Example

Console.WriteLine( "Enter your age:" );
int age = Console .ReadLine();
Console.WriteLine( "Your age is: " + age );


The error message will be something like this:


Cannot implicitly convert type 'string' to 'int'





Like the error message says, you cannot implicitly convert type 'string' to 'int'.

Luckily, for you, you just learned from the previous chapter (Type Casting), that you can convert any type explicitly, by using one of the Convert.To methods:


Example

Console.WriteLine( "Enter your age:" );
int age = Convert.ToInt32( Console. ReadLine());
Console.WriteLine( "Your age is: " + age );




Note: If you enter wrong input (e.g. text in a numerical input), you will get an exception/error message (like System.FormatException: 'Input string was not in a correct format.').

You will learn more about Exceptions and how to handle errors in a later chapter.

C# Operators

Operators

Operators are used to perform operations on variables and values.

In the example below, we use the + operator to add together two values:


Example

int x = 100 + 50 ;




Although the + operator is often used to add together two values, like in the example above, it can also be used to add together a variable and a value, or a variable and another variable:


Example

int sum1 = 100 + 50 ; // 150 (100 + 50)
int sum2 = sum1 + 250 ; // 400 (150 + 250)
int sum3 = sum2 + sum2 ; // 800 (400 + 400)



Arithmetic Operators

Arithmetic operators are used to perform common mathematical operations:

Operator

Name

Description

Example

+     

 Addition     

 Adds together two values     

 x+y     
-    

 Subtraction     

 Subtracts one value from another     

 x-y    
*    

 Multiplication     

 Multiplies two values     

 x*y    
/    

 Division     

 Divides one value by another     

 x/y    
%    

 Modulus     

 Returns the division remainder     

 x%y    
++    

 Increment     

 Increases the value of a variable by 1     

 x++    
--    

 Decrement     

 Decreases the value of a variable by 1     

 x--    


Assignment Operators

Assignment operators are used to assign values to variables.

In the example below, we use the assignment operator (=) to assign the value 10 to a variable called x:


Example

int x = 10 ;




The addition assignment operator (+=) adds a value to a variable:


Example

int x = 10 ;
x+=5;



A list of all assignment operators:

Operator     Example     Same as    
=    

 x=5    

 x=5    
+=    

 x+=3    

 x=x+3    
-=    

 x-=3    

 x=x-3    
*=    

 x*=3    

 x=x*3    
/=    

 x/=3    

 x=x/3    
%=    

 x%=3    

 x=x%3    
&=    

 x&=3    

 x=x&3    
|=    

 x|=3    

 x=x|3    
^=    

 x^=3    

 x=x^3
>>=    

 x>>=3    

 x=x>>3    
<<=     

 x<<=3     

 x=x<<3     


Comparison Operators

Comparison operators are used to compare two values (or variables). This is important in programming, because it helps us to find answers and make decisions.

The return value of a comparison is either True or True. These values are known as Boolean values, and you will learn more about them in the Booleans and If..Else chapter.

In the following example, we use the greater than operator (>) to find out if 5 is greater than 3:


Example

int x = 5 ;
int x = 3 ;
Console.WriteLine( x > y ); // returns True because 5 is greater than 3



A list of all comparison operators:

Operator     Name     Example    
==    

 Equal to    

 x==y    
!=    

 Not equal    

 x!=y    
>    

 Greater than    

 x>y    
<    

 Less than    

 x< y     
>=    

 Greater than or equal to    

 x>=y    
<=     

 Less than or equal to    

 x<= y    


Logical Operators

As with comparison operators, you can also test for True or False values with logical operators.

Logical operators are used to determine the logic between variables or values:

Operator     Name     Description     Example    
&&   

 Logical and   

 Returns True if both statements are true   

 x<5 && x<10    
||   

 Logical or   

 Returns True if one of the statements is true   

 x<5 || x<4   
!   

 Logical not   

 Reverse the result, returns False if the result is true   

 !(x<5 && x< 10)   


You will learn more about comparison and logical operators in the Booleans and If...Else chapters.

C# Math

The C# Math class has many methods that allows you to perform mathematical tasks on numbers.

Math.Max(x,y)

The Math.Max(x,y) method can be used to find the highest value of x and y:


Example

Math.Max(5,10);




Math.Min(x,y)

The Math.Min(x,y) method can be used to find the lowest value of x and y:


Example

Math.Min(5,10);




Math.Sqrt(x)

The Math.Sqrt(x)method returns the square root of x:


Example

Math.Sqrt(64);




Math.Abs(x)

The Math.Abs(x)method returns the absolute (positive) value of x:


Example

Math.Abs(-4.7);




Math.Round()

The Math.Round(x)rounds a number to the nearest whole number:


Example

Math.Round(99.9);




C# Strings

C# Strings

Strings are used for storing text.

A string variable contains a collection of characters surrounded by double quotes:


Example

Create a variable of type string and assign it a value:

string greeting="Hello";




A string variable can contain many words, if you want:


Example

string greeting2="Nice to meet you!";




String Length

A string in C# is actually an object, which contain properties and methods that can perform certain operations on strings. For example, the length of a string can be found with the Length property:


Example

string txt="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
Console .WriteLine( "The length of the txt string is: " + txt . Length );




Other Methods

There are many string methods available, for example ToUpper() and ToLower(), which returns a copy of the string converted to uppercase or lowercase:


Example

string txt="Hello World";
Console .WriteLine( txt .ToUpper()); // Outputs "HELLO WORLD"
Console .WriteLine( txt .ToLower()); // Outputs "hello world"




C# Booleans

C# Booleans

Very often, in programming, you will need a data type that can only have one of two values, like:

• YES / NO

• ON / OFF

• TRUE / FALSE


For this, C# has a bool data type, which can take the values true or false.

Boolean Values

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


Example

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




However, it is more common to return boolean values from boolean expressions, for conditional testing (see below).

Boolean Expression

A Boolean expression returns a boolean value: True or False, by comparing values/variables.

This is useful to build logic, and find answers.

For example, you can use a comparison operator, such as the greater than (>) operator to find out if an expression (or a variable) is true:


Example

int x=10;
int y=9;
Console .WriteLine( x>y); // returns True, because 10 is higher than 9




Or even easier:


Example

Console .WriteLine( 10>9); // returns True, because 10 is higher than 9




In the examples below, we use the equal to (==) operator to evaluate an expression:


Example

int x=10;
Console .WriteLine( x==10); // returns True, because the value of x is equal to 10





Example

Console .WriteLine( 10==15); // returns False, because 10 is not equal to 15




Real Life Example

Let's think of a "real life example" where we need to find out if a person is old enough to vote.

In the example below, we use the >= comparison operator to find out if the age (25) is greater than OR equal to the voting age limit, which is set to 18:


Example

int myAge=25;
int votingAge=18;
Console .WriteLine( myAge>=votingAge);




Cool, right? An even better approach (since we are on a roll now), would be to wrap the code above in an if...else statement, so we can perform different actions depending on the result:


Example

Output "Old enough to vote!" if myAge is greater than or equal to 18. Otherwise output "Not old enough to vote.":

int myAge=25;
int votingAge=18;

if (myAge>=votingAge)
{
Console .WriteLine( "Old enough to vote!");
}
else
{
Console .WriteLine( "20 is greater than 18");
}




The boolean value of an expression is the basis for all C# comparisons and conditions.

You will learn more about conditions (if...else) in the next chapter.

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