Learning C# 3.0

Relational Operators

Relational operators compare two values and then return a Boolean value (true or false, as described in Chapter 3). The greater than operator (>), for example, returns true if the value on the left of the operator is greater than the value on the right. Thus, 5>2 returns the value true, whereas 2>5 returns the value false.

The relational operators for C# are shown in Table 4-1. This table assumes two variables: bigValue and smallValue, in which bigValue has been assigned the value 100, and smallValue the value 50.

Table 4-1. C# relational operators (assumes bigValue = 100 and smallValue = 50)

Name	Operator	Given this statement	The expression evaluates to
Equals	==	bigValue == 100 bigValue == 80	True False
Not equals	!=	bigValue != 100 bigValue != 80	False True
Greater than	>	bigValue > smallValue	True
Greater than or equal to	>=	bigValue >= smallValue smallValue >= bigValue	True False
Less than	<	bigValue < smallValue	False
Less than or equal to	<=	smallValue <= bigValue bigValue <= smallValue	True False

Each of these relational operators acts as you might expect. Notice that most of these operators are composed of two characters. For example, the “greater than or equal to” operator (>=) is made up of the greater-than symbol (>) and the equals sign (=). The symbols must appear in that order for the operator to be valid; =< isn’t a valid operator, and => is a different operator altogether, but one you won’t see until much later in the book.

Notice also that the equals operator is made up of two equals signs (==) because the single equals sign alone (=) is reserved for the assignment operator.

Warning

A very common beginner mistake is to confuse the assignment operator (=) with the equals operator (==). Even experienced programmers do this from time to time. Just remember that the latter has two equals signs, and the former only one.

The C# equals operator (==) tests for equality between the objects on either side of the operator. This operator evaluates to a Boolean value (true or false). Thus, the statement:

myX == 5;

evaluates to true if and only if the myX variable has a value of 5.