Zero decimal representation for negative Numerator and Denominator

[iiwaasnet]

Rational created with negative numerator and denominator gives 0 when casting to decimal. Isn't it a bug?

var num = new Rational(-9, -3);
var dec = (decimal) num;  // dec is 0

[iiwaasnet]

Yet another case:

num = new Rational(9, 3);
var approximate = Rational.Approximate(-0.1m, Decimal.Zero);
num += approximate;

dec = (decimal) num; // dec is 0