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Programming C# 4.0 by Jesse Liberty, Matthew Adams, Ian Griffiths

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Expressions and Statements

An expression is a piece of code that produces a value of some kind. We’ve actually seen several examples already, the most basic being the numbers we’re assigning into the variables. So in our example, a number such as:

5.141

is an expression. Expressions where we just tell C# what value we want are called literal expressions. More interestingly, expressions can perform calculations. For example, we could calculate the distance traveled per kilogram of fuel consumed with the expression in Example 2-6.

Example 2-6. Dividing one variable by another

kmTravelled / fuelKilosConsumed

The / symbol denotes division. Multiplication, addition, and subtraction are done with *, +, and -, respectively.

You can combine expressions together too. The / operator requires two inputs—the dividend and the divisor—and each input is itself an expression. We were able to use variable names such as kmTravelled because a variable name is valid as an expression—the resultant value is just whatever that variable’s value is. But we could use literals, as Example 2-7 shows. (A trap awaits the unwary here; see the sidebar on the next page.)

Example 2-7. Dividing one literal by another

60 / 10

Or we could use a mixture of literals and variable names to calculate the elapsed time in minutes:

elapsedSeconds / 60

or a multiplication expression as one of the inputs to a division expression to calculate the elapsed time in hours:

elapsedSeconds / (60 * 60)

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