Stephens' C# Programming with Visual Studio® 2010 24-Hour Trainer

Performing Calculations



137

Operands and Operators

One issue that confuses some people is the fact that C# uses the data types of an expression’s operands

to determine the way the operators work. If an expression contains two integers, the operators use

integer arithmetic. If an expression contains two floats, the operators use floating-point arithmetic.

Sometimes this can lead to confusing results. For example, the following code tries to save the

value 1/7 in the

float variable ratio. The values 1 and 7 are integers so this calculation uses

integer division, which discards any remainder. Because 1 / 7 = 0 with a remainder of 1,

ratio is

assigned the value 0, which is probably not what you intended.

float ratio = 1 / 7;

To force C# into using floating-point division, you can convert the numbers into the float data

type. The following code uses the

F suffix character to indicate that 1 and 7 should have the float

data type instead of

int. Now the program performs floating-point division so it assigns ratio the

value 0.142857149 (approximately).

float ratio = 1F / 7F;

Instead of using data type prefixes, you can also use casting to make the program treat the values as

floats as in the following code:

float ratio = (float)1 / (float)7;

Promotion

If an expression uses two different data types, C# promotes the one with the more restrictive type.

For example, if you try to divide an

int by a