C# Operators

An operator is a sign that makes a value from other values. The sign + is an operator, and so are the signs that change or combine values.

Up and down by one

The ++ sign adds 1 to count. The -- sign then takes 1 away again.

using System;

class Program
{
    static void Main(string[] args)
    {
        int count = 5;
        count++;
        Console.WriteLine(count);
        count--;
        Console.WriteLine(count);
    }
}

Short update signs

The += sign adds 4 to score. The *= sign then multiplies the new score by 3.

using System;

class Program
{
    static void Main(string[] args)
    {
        int score = 6;
        score += 4;
        Console.WriteLine(score);
        score *= 3;
        Console.WriteLine(score);
    }
}

Joining bool tests

The && sign gives true because both sides are true. The || sign also gives true, and ! flips the first value to false.

using System;

class Program
{
    static void Main(string[] args)
    {
        bool isSunny = true;
        bool isWarm = true;
        Console.WriteLine(isSunny && isWarm);
        Console.WriteLine(isSunny || isWarm);
        Console.WriteLine(!isSunny);
    }
}

Parentheses set the order

Multiplication runs before addition in the first line. Parentheses in the second line make the addition run first.

using System;

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine(2 + 3 * 4);
        Console.WriteLine((2 + 3) * 4);
    }
}

Example

using System;

class Program
{
    static void Main(string[] args)
    {
        int items = 3;
        items += 2;
        Console.WriteLine("Items: " + items);
        double price = 4.5;
        double total = items * price;
        Console.WriteLine("Total: " + total);
        bool bigOrder = items > 4 && total > 20;
        Console.WriteLine("Big order: " + bigOrder);
    }
}

Key points

The sign ++ adds 1 to a variable, and -- takes 1 away.
The sign += adds a value to a variable in one step.
The sign *= multiplies a variable by a value in one step.
The sign && gives true only when both sides are true.
The sign || gives true when at least one side is true.
The sign ! flips true to false and false to true.
Parentheses set the order of a calculation, just like in maths.

In this example, items starts at 3 and += 2 raises it to 5, so the first line prints Items: 5. The total multiplies 5 items by the price 4.5, and the second line prints Total: 22.5. Both tests in the last line are true, so it prints Big order: True.

Try it Yourself

Edit the code, then press Run.

Running is simulated · Programiz C# Compiler

using System;

class Program
{
    static void Main(string[] args)
    {
        int items = 3;
        items += 2;
        Console.WriteLine("Items: " + items);
        double price = 4.5;
        double total = items * price;
        Console.WriteLine("Total: " + total);
        bool bigOrder = items > 4 && total > 20;
        Console.WriteLine("Big order: " + bigOrder);
    }
}

Exercise

What does score hold after int score = 10; and then score += 5;?

15 10 5 105