Question

May be this is a very basic question, but I am really interested to know what really happens.

For example if we do the following in c#:

object obj = "330.1500249000119";
var val = Convert.ToDouble(obj);

The val becomes: 330.15002490001189

The question is that why the last 9 is replace by 89? Can we stop it from happening this way? And is this precision dependent on the Current Culture?

Answer 1

This has nothing to do with culture. Some numbers can not be exactly represented by a base-2 number, just like in base-10 1/3rd can’t be exactly represented by .3333333

Note that in your specific case you are putting in more digits than the data type allows: the significant digits available with a Double is 15-16 (depending on range), which your number goes beyond.

Instead of a Double, you can use a Decimal in this case:

object obj = "330.1500249000119";
var val = Convert.ToDecimal(obj);