1.4.15 Boolean Expressions

You already know the Boolean type:

bool

and its two values:

true
false

A Boolean expression is an expression that C# evaluates as a Boolean value.

That means its result is:

true

or:

false

Suppose the Player class contains:

public bool isAvailable;

Then this expression:

player1.isAvailable

already produces a Boolean value.

If the field currently contains true, the expression evaluates to true.

If it currently contains false, the expression evaluates to false.

Consider:

public void SetAvailability(bool available)
{
    this.isAvailable = available;
}

Inside the method:

available

is a Boolean parameter.

Because its type is bool, using:

available

as an expression produces the Boolean value supplied by the caller.

For example:

player1.SetAvailability(true);

means that during the call:

available = true

A simple decision can use an existing Boolean expression:

if (player1.isAvailable)
{
    System.Console.WriteLine("Player is available.");
}

The condition:

player1.isAvailable

must evaluate to true or false.

The if statement uses that result to choose whether its block runs.

In:

if (player1.isAvailable)
{
    System.Console.WriteLine("Player is available.");
}

the Boolean expression is:

player1.isAvailable

The if statement is the decision structure that uses the expression.

These are Boolean values:

true
false

They can appear where a Boolean value is required.

For example:

player1.isAvailable = true;

Suppose the debugger shows:

player1.isAvailable = false

At:

if (player1.isAvailable)

you can predict that the condition evaluates to false.

The if block will therefore be skipped.

This connects:

• NNew
• CChanged
• RRemoved