public float GetGradesAverageInGroup(Group studentGroup)
{
float retVal = 0;
int studentsCount = 0;
ICollection <Student> students = studentsRepository.GetStudentsByGroupId(studentGroup.Id);
foreach (Student student in students)
{
studentsCount++;
retVal += GetStudentGradesAverage(student);
}
if (studentsCount > 0)
{
retVal = retVal / studentsCount;
}
return(retVal);
}