Why this function always returns zero?

Question

This is the function:

private decimal? CalculateMe(int? kat0, int? kat1, int? kat2, int? numberOfPlants)
{
    if (numberOfPlants == null || numberOfPlants == 0 || kat0 == null || kat1 == null || kat2 == null)
        return null;

    return ((kat1 + kat2 * 2) / (numberOfPlants * 2)) * 100;
}

This function always returns zero! Even if an explicit cast is written Convert.ToDecimal, the function returns zero.

return Convert.ToDecimal(((kat1 + kat2 * 2) / (numberOfPlants * 2)) * 100);

Can you provide some samples? Using `/` on an `int` with an outcome of less than 0 will always result in 0. — Dion V., Apr 03 '15 at 14:17
You know in this (kat1 + kat2 * 2) the "kat2 * 2" will be done first. I would add parenthesis to make it more clear. — JBrooks, Apr 03 '15 at 14:21

score 1 · Accepted Answer · answered Apr 03 '15 at 14:17

Because the operator / with two ints as operands always performs an integer division.

If you want to perform a real division, you need to convert the operands to a non-integer numeric type (float, double, decimal). In other words, you have to perform the conversion before the division happens, not afterwards.

score 0 · Answer 2 · answered Apr 03 '15 at 14:18

0

You need to cast each of your operands to get that to work, i.e.:

  return ((decimal)(kat1 + kat2 * 2) / (decimal)(numberOfPlants * 2)) * 100;

answered Apr 03 '15 at 14:18

Darkseal

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No you don't. All you need to do is cast ONE of the variables as *decimal*, *float* or *double*. The rest will be implicitly cast. – Sani Huttunen Apr 03 '15 at 14:20

score 0 · Answer 3 · answered Apr 03 '15 at 14:18

0

You operate on integer. Ex : 1/3 = 0 (if 1 and 3 are int).

You should use others types (decimal or float, etc).

answered Apr 03 '15 at 14:18

antoinestv

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Why this function always returns zero?

3 Answers3