Math.Floor vs cast to an integral type in C#

Question

Are there any reasons one would prefer to use Math.Floor vs casting to an integral type?

double num;
double floor = Math.Floor(num);

OR

Answer 1

Math.Floor is a fundamentally different operation from truncation because it handles negative numbers differently. Math.Floor(-1.5) == -2.0, while (int)-1.5 == -1.