Working with objects in array-need help

Question

Hi, im doing very simple app and i wanna create array of sudents(std) and each std has array(3) grades-grade is a class as well.So each std has array of grades.Each grade has name and stdGrade.So each std has arrray of grade objects.Im trying to init std: GradeClass[] stdGradeArr = new GradeClass[3]; Console.WriteLine("Std Grade for Math"); stdGradeArr [0].StdGrade = int.Parse (Console.ReadLine()); and i get error:obj ref not set to an instance of obj...