Unary Operators in C#

(Last Updated On: January 29, 2019)

Unary operators in C# language is used to increment / decrement the value of a variable or to negate the value of a Boolean variable / Expression etc. Unary operator is performed on only one operand / variable.

Sounds difficult, in fact it’s very easy…Keep reading!!!

We are going to learn about below unary operators in simple way with examples.

++, — and ! (negate) unary operators.

 

Unary Operators in C# and their operations

++ Increment operator that increment the value by 1
— Decrement operator that decrement the value by 1
! Negate the Boolean value

 

Note that ! operator also comes under logical operators in C# programming.

 

Unary operators require only one operand, meaning, unary operators are performed on only one variable.
For example,

If statement is as, int n = 10;
Then, ++ unary operator can be applied on variable n to increment its value by 1 from 10 to 11 as below
n++;

Similarly, — can be applied on variable n to decrement its value by 1 from 10 to 9 as below
n–;

 

++ ( Increment) Unary operator in C# with Code

++ operator increment the value of variable by 1. For example, in below program, value on n is initialized to 5.
We have applied ++ unary operator on variable n in next statement, that increment the value of n by 1 resulting 6.

On printing the value of variable n, output will be 6.

Output:
6

 

Pre Increment & Post increment Unary operators in C#

There are two ways, we can apply ++ operator on variable n,

1)Pre-increment e.g. ++n; //apply ++ before variable n.
2)Post increment e.g. n++ // Apply ++ after the variable n.

 

PRE-INCREMENT

Pre-increment, first increment the value of a variable, then perform operation.

What does it mean?

Let’s consider the statement b = ++n; in below program.

First increment will be performed. Meaning, first value of n will be incremented then assign the incremented value to variable b.

Hence, if value of n is initially 5, then first it will be incremented to 6 then it will be assigning to b.

So, value of b will be 6.

Note that value of n will also be 6 as it has already been incremented. So, if you print the value on n, it will print 6.

Output:
6

POST-INCREMENT

post increment is just opposite to pre-increment, first value of n will be assigned to variable b, then n will be incremented.

So, value of variable b will be 5.

Then increment happens on n, so if you print the value on n, it’s value will be 6.

Output:
5
6

 

CONFUSION:

In below program, why the value of n is same i.e.6 when, whatever we write ++n or n++?

Output:

6

Answer: Because, on statement ++n or n++, we are not performing any operation, for example, in previous example we did “b = ++n,” or “b =n++;”

We are just incrementing the value by applying any pre-increment [++n] or post increment[n++].

Hence, in next statement, during printing, we are getting incremented value of variable n.

 

NOTE:

++n or n++ can also be written as n += 1; Notice first +, then = symbol together.

n +=1; is same as n = n+1;

Example:

Output:
6

 

— Unary Operator in C# with Code

— Unary operator decrements the value of a variable by 1.

NOTE: All the rules we studied for ++ unary operator will be applied to – unary operator too. So, just using – instead of ++ in all above examples, you can practice and see the result.

Just an example here.

For example, in below program, value on n is initialized to 5.

We have applied — unary operator on variable n in next statement, that decrement the value of n by 1 resulting 4.

On printing the value of variable n, output will be 4.

Output:
4

In brief,

PRE-DECREMENT

–n,

POST-DECREMENT

n–;

n– or –n can be written as n -= 1. It is same as n = n -1.

 

! (Negate) Unary operator

! negate unary operator just used to reverse/ invert a Boolean value.

It is applied on Boolean variable or Boolean expression.

! Example on Boolean variable.

In the code example, a Boolean variable isDiscount has been created and initialized to false.

In Console.WriteLine isDiscount has been inverted using ! i.e. !isDiscount resulting output as true.

Output:
true

! Example on Boolean Expression.

In this code example, result is of Boolean type and initialized with value false.

C > b; is a Boolean expression, as it compares if c is greater that b resulting true or false.

In this example, value of b is 10 and value of c is 20. So, the expression c > b will result true and true will be assign to variable result.

On negating the variable “result” in Console.WriteLine method as !result, the output will be false.

Output:
False

SPECIAL NOTE:

– is also treaded as Unary operator in some case besides arithmetic operator in C# language.

– unary operator is used to negate the value of a variable.

For example, if variable n has value 10 and you want to assign 10 in another variable b;

Then you can write the statement as b = -n;, Now, b will have value -10.

Note that the value of n will not be changed and it will be 10 only.

 

RECAP:

Unary operators in C#

++ , — and ! are unary operators in C# programming
++ unary operator increments the value of a variable by 1, it has two form Pre-increment(++n) and post increment (e.g. n++) form
n++ or ++n can be written as n += 1. It is same as n = n +1.

Pre- increment will increment the value of a variable first, then operate it.
In post increment the operation will happen first, then value will be increment.

— decrement the value of a variable by 1.
— unary operator also has two form PRE-DECREMENT i.e.–n, and POST-DECREMENT i.e. n–;
n– or –n can be written as n -= 1. It is same as n = n -1.

! negate unary operator just used to reverse/ invert a Boolean value.