Else statements

An else statement allows us to run a block of code if the previous if (or else if) condition was false.

We can write this using words like this:

• Check condition:
  • If condition is true, run the code inside the if block.
  • If condition is false, run the code inside the else block.

Basic syntax

if (condition) {
    // Code to run if the condition is true
} else {
    // Code to run if the condition is false
}

Or, if we’re using else if statements:

if (condition1) {
    // Code to run if condition1 is true
} else if (condition2) {
    // Code to run if condition1 is false and condition2 is true
} else if (condition3) {
    // Code to run if condition1 and condition2 are false and condition3 is true
} else {
    // Code to run if all previous conditions are false
}

else’s relationship with else if statements

You may be able to tell that an else if statement is actually just syntax sugar for an if statement wrapped inside an else block.

This code:

if (condition1) {
    // Code to run if condition1 is true
} else if (condition2) {
    // Code to run if condition1 is false and condition2 is true
}

Is exactly the same as this code:

if (condition1) {
    // Code to run if condition1 is true
} else {
    if (condition2) {
        // Code to run if condition1 is false and condition2 is true
    }
}

…but much easier to read and write!

Our example from before: positive, negative, or zero

In the last chapter, we wrote this code:

int number = -5;
if (number > 0) {
    Console.WriteLine("The number is positive.");
} else if (number < 0) {
    Console.WriteLine("The number is negative.");
} else if (number == 0) {
    Console.WriteLine("The number is zero.");
}

We worked out that, if the number is not greater than zero, and not less than zero, it must, well, be zero!

So there really is no need to check the last condition.
We can just use an else statement instead:

int number = -5;
if (number > 0) {
    Console.WriteLine("The number is positive.");
} else if (number < 0) {
    Console.WriteLine("The number is negative.");
} else {
    Console.WriteLine("The number is zero.");
}

Output:

The number is negative.

Or, if we set number to 0:

The number is zero.