What is the error in below code? Why can't I convert it to int

Question

int age=0;
age=Convert.ToInt32(DateTime.Now-this.dateOfBirth);

Answer 1

public int CalculateAge()
{
int age=0;
age =
Convert.ToInt32(DateTime.Now-this.dateOfBirth);
return age;
}

this.dateOfBirth is a parameter passed to Constructor

Answer 2

hey amith if you don't mind showing the piece of code at large that might help clear somethings