We all need a refresher on the basics. I’ve covered data types before, but the hierarchy below sums it up in a clear diagram:
At the leafs, the float vs Integral is clearly shown. Integrals (Integer) are viewed as subset of the real numbers, they are numbers that can be written without a fractional or decimal component. For example, 65, 7, and −756 are integers; 1.6 and 1½ are not integers. The set of all integers is often denoted by a boldface Z.
The C# standard only lists double and float as floating points available (those being the C# shorthand for System.Double and System.Single), but strictly speaking the decimal type (shorthand for System.Decimal) is also a floating point type.
The decimal type is just another form of floating point number - but unlike float and double, the base used is 10. Compared to floating-point types, the decimal type has more precision and a smaller range, which makes it appropriate for financial and monetary calculations.
Financial Issue Testing
Let’s review financial situations. Say we are using floats to track the money.
123,456.78 + 123.45 = $123,580.2 --> should calculate to $123,580.23
What happen – float only can support 7 digits, so C# converted number to 123456.8 + 123.45 – since last digit is 5 or less – it rounded down. If the number would of ended in a 6 or above – it would of rounded up. Lost $0.03 – do this to many times in your shopping cart and it will add up.
Do you have financial reports for month/year end?
float x1 = float.Parse("1234567890.12"); //1.234568E+9
x1.ToString(); //"1.234568E+09"
oops… off by over $110 bucks. Use decimal type for financial fields.
Stress testing float – double - decimal
--------- Show limits of float ----------------
123.4567
float = 123.4567, double = 123.4567, decimal = 123.4567
123.45678
float = 123.4568, double = 123.45678, decimal = 123.45678
--------- Show limits of double ----------------
123.456789012345
float = 123.4568, double = 123.456789012345, decimal = 123.456789012345
123.4567890123456
float = 123.4568, double = 123.456789012346,
decimal = 123.4567890123456
--------- Show limits of decimal ----------------
123.45678901234567890123456789
float = 123.4568, double = 123.456789012346, decimal = 123.45678901234567890123456789
123.456789012345678901234567899
float = 123.4568, double = 123.456789012346, decimal = 123.45678901234567890123456790