Combine conditions with logical operators

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Sometimes a single condition isn't enough to make a decision. You might want to check whether two things are both true, or whether at least one of them is true. C#'s logical operators let you combine multiple conditions into one expression.

The three logical operators

Operator	What it does	Example	Result
&&	true only if both sides are true	true && false	false
||	true if at least one side is true	true || false	true
!	Flips a Boolean value	!true	false

Using && (all conditions must be met)

Use && when every condition must be met to run a block of code:

int age = 20;
bool hasTicket = true;

if (age >= 18 && hasTicket)
{
    Console.WriteLine("Entry granted.");
}
else
{
    Console.WriteLine("Entry denied.");
}

Using || (at least one condition must be met)

Use || when any one condition is enough to run a block of code:

bool isWeekend = false;
bool isHoliday = true;

if (isWeekend || isHoliday)
{
    Console.WriteLine("The office is closed.");
}

Using ! (reverse a condition)

The ! operator reverses a Boolean value. It's useful for checking the absence of a condition:

bool isLoggedIn = false;

if (!isLoggedIn)
{
    Console.WriteLine("Please log in to continue.");
}

Combining operators

You can combine &&, ||, and ! in a single expression. Use parentheses to group conditions and make your code easier to read:

int roll1 = 6, roll2 = 6, roll3 = 5;

if ((roll1 == roll2) || (roll2 == roll3) || (roll1 == roll3))
{
    Console.WriteLine("You rolled doubles!");
}

Here, three comparisons are combined with ||, so the message displays if any two of the three dice match. In the next unit, you use this expression to build a dice game.