C# For Beginners

Searchâ€¦

Lesson 4: Operators

At the end of this lesson, you should be able to answer the following:

- What is an operator?
- What is an expression?
- What are some of the commonly used operators in C#?

In the previous lesson, we mentioned that the type of a value can determine the *operations* that can be performed with it.

For example, we can add two integers:

1

10 + 2

Copied!

The *operator*. It represents an action or operation that can be done to the values supplied with it. The

`+`

symbol between the two numbers is an `+`

operator here is the same used in arithmetic addition.The whole line above is called an *expression*. An expression can be evaluated further by C# to produce a new value.

Type the line into your code box and run the program. You'll see that C# evaluates the expression and displays the result.

Why did it display the result even if we didn't call

`Console.WriteLine()`

? Dotnet Interactive is also a REPL - an environment that allows quick evaluation of an expression, after which the output is displayed.

If we write more than one statement in the code box, it won't be a single expression anymore and instead of doing the read-evaluate-print loop, Dotnet Interactive will compile the program as a whole.

We can also do subtraction, multiplication, and division - they each have their own operator.

1

10 - 2 // subtraction

Copied!

1

10 * 2 // multiplication

Copied!

1

10 / 2 // division

Copied!

Type each line above in the code box one at a time and run the program each time. The output will be the result of the arithmetic expression.

If you try to write all of them at the same time and run the program, you'll get an error.

1

10 + 2;

2

10 - 2;

3

10 * 2;

4

10 / 2;

Copied!

Even if we put semicolons at the end of each line, the program will still be invalid!

That's because expressions are not valid statements. As we learned in Lesson 1, C# programs are made of statements. Expressions in C# programs must be used as part of a valid statement.

What's a statement we've already learned? Why, the **print** statement of course!

Wrap each expression into a

`Console.WriteLine()`

call.1

Console.WriteLine(10 + 2);

2

Console.WriteLine(10 - 2);

3

Console.WriteLine(10 * 2);

4

Console.WriteLine(10 / 2);

Copied!

The result of each expression is now displayed.

Here are the common operators in C#.

Arithmetic Operators

These operators work with numeric values.

Operator

Description

Example

`+`

Addition

`17 + 18`

`-`

Subtraction

`65 - 21`

`*`

Multiplication

`12 * 4`

`/`

Division

`60 / 15`

`%`

Remainder (modulo)

`20 % 3`

Comparison Operators

These operators compare two values. The result will either be

`true`

or `false`

.Operator

Description

Example

`>`

Greater than

`5 > 2`

`<`

Less than

`1 < 7`

`>=`

Greater than or equal to

`9 >= 6`

`<=`

Less than or equal to

`1000 < 84`

`==`

Equal to

`"apple" == "orange"`

`!=`

Not equal to

`"apple" != "orange"`

Logical Operators

Operator

Description

Example

`&&`

Logical AND

`true && false`

`||`

Logical OR

`false || true`

`!`

Logical NOT

`!false`

Is the following an expression? Why or why not?

1

"100 + 25"

Copied!

True or False: An expression by itself is a valid statement.

Wrap each example in the tables above into a

`Console.WriteLine()`

statement. Can you guess what each result will be?Last modified 4mo ago

Copy link