Question

Convert.ToDouble is adding zeros and 1 like in this picture:

Why it is turning from 21.62 to 21.620000000000001 ?
Is this about floating point issue?

Answer 1

Double (and Float) are floating-point types, and in a binary system will have some imprecision.

If you need more precise comparisons use decimal instead. If you’re just doing calculations double should be fine. If you need to compare doubles for absolute equiality then compare the absolute value of the difference to some small constant:

if (a == b)  // not reliable for floating point
{ 
    ....
}

double EPSILON = 0.0000001;
if (Math.Abs(a-b) < EPSILON)
{
    ....
}